Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, and electrons. All atoms.

Name: Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, and electrons. All atoms.
Uploaded: 2017-08-20T16:21:50+00:00
Duration: PTM30S41
Channel: Franklin Hart
Description: Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, and electrons. All atoms.

Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, and electrons. All atoms of the same element contain the same number of protons (and electrons) but may vary in the number of neutrons (isotopes).

Protons and neutrons are found inside the tiny but dense nucleus, whereas electrons are found in orbitals outside the nucleus. The arrangement of electrons in the orbitals is called the electronic configuration and determines the chemistry of an atom. The different types of atoms are called elements, which are arranged systematically in the periodic table. Having eight valence electrons is particularly desirable (“the octet rule”).

All matter is composed of indivisible atoms.
John Dalton ( ) The Atomic Theory Dalton’s Atomic Theory All matter is composed of indivisible atoms. All atoms of one element are identical to each other but different than the atoms of other elements. Compounds are formed when atoms of different elements combine in whole number ratios. Atoms are rearranged during chemical reactions but atoms cannot be created or destroyed.

Definitions 2H2 (g) + O2 (g)  2H2O(g) 2C(s) + O2 (g)  2CO(g)
Law of conservation of matter states that matter is neither lost nor gained during a chemical reaction. Ex. 2H2 (g) + O2 (g)  2H2O(g) 2C(s) + O2 (g)  2CO(g) Law of definite proportions states that in a compound, the constituent elements are always present in a definite proportion by weight. Ex. Pure water, a compound, is always made up of 11.2% hydrogen and 88.8% oxygen by weight or table sugar always contains 42.1% carbon, 6.5% hydrogen, and 51.4% oxygen by weight.

Structure of the Atom Components Positive protons, negative electrons, and neutral neutrons Atomic Number The number of protons in an atom, which determines what element it is Mass Number Number of protons + the number of neutrons

Definitions Protons are positively charged subatomic particles found in the nucleus. Electrons are negatively charged subatomic particles found in the space around the nucleus. Neutrons are electrically neutral subatomic particles found in the nucleus. Nucleus is the small central core of the atom: contains the protons and neutrons.

Separation of alpha, beta, and gamma particles by applying an electric field.
Ernest Rutherford Gold foil experiment. A beam of positively charged alpha particles hits the gold foil. Most particles passed straight, some slightly deflected and some deflected back. The reason for deflection were the positions of the nucleus.

Ernest Rutherford ( ) Rutherford’s interpretation of the gold foil experiment done by Geiger and Marsden.

Modern View of the Atom For an atom, which always has no net electrical charge, the number of negatively charged electrons around the nucleus equals the number of positively charged protons in the nucleus.

Scientists have been able to obtain computer-enhanced images of the outer surface of atoms using the scanning tunneling microscope (STM) and the atomic force microscope (AFM).

Structure of the Atom Isotopes Isotopes of the same element have the same number of protons and electrons but differ in the number of neutrons. Atomic Mass The atomic mass for each element on the periodic table reflects the relative abundance of each isotope in nature.

Definitions Atomic number is the number of protons in the nuclei of the atoms of an element Mass number or atomic mass is the number of neutrons plus number of protons in the nucleus of an atom Mass number = #’s of protons + #’s of neutrons Ex. How many protons, neutrons, and electrons are in atom of gold (Au) with a mass number of 197? Protons = 79; Electrons = 79; Neutrons = 197 – 79 = 118; Isotopes are atoms of the same element having different mass numbers.

Definitions cont Atomic mass unit (amu) is the unit for relative atomic masses of the elements; 1 amu =1/12 the mass of carbon-12 isotope. 1 amu = x10-24 grams Atomic weight is the number that represents the average atomic mass of the element’s isotopes weighted by percentage abundance.

Isotopes 1 2 3 H H H 1 1 1

Learning Check Write the nuclear symbols for atoms with the following subatomic particles. A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 47 e- ___________

Solution A. 8 p+, 8 n, 8 e- 16O 8 B. 17p+, 20 n, 17e- 37Cl 17
C. 47p+, 60 n, 47 e- 107Ag 47

Learning Check 1. Which of the following pairs are isotopes of the same element? 2. In which of the following pairs do both atoms have 8 neutrons? A. 15X 15X B. 12X 14X C. 15X 16X

Solution B. 12X 14X Both nuclear symbols represent isotopes of carbon with six protons each, but one has 6 neutrons and the other has 8. C. 15X 16X An atom of nitrogen (7) and an atom of oxygen (8) each have 8 neutrons.

Isotopes of Magnesium 24Mg 25Mg 26Mg In naturally occurring magnesium,
there are three isotopes. Isotopes of Mg 24Mg 25Mg 26Mg

Relative Masses of Atoms
Use atomic weights of the elements to calculate molecular weights (MW) of compounds Relative masses provide a simple way of comparing the masses of atoms. Ex. The mass of neon atoms is and the mass of calcium atoms is

The exact relationship between two masses calculated
Ca atom mass 40.08 = = 1.986 Mass of Calcium is 2x than Ne Ne atom mass 20.18 He atom mass 4.003 = = 3.971 Mass of Helium is 4x than Hydrogen H atom mass 1.008

Calculating the atomic weight of compounds
MW = CnHmOk MW = n(at. Wt. C) + m(at. Wt. H) + k(at. Wt. O) H2O the MW is MW = 2(at. Wt. H) + 1(at. Wt. O) MW = 2(1.008 u) + 1( u) MW = u or u for water

Learning Check Use atomic weighs from the periodic table inside the front cover of your book to determine the molecular weight of urea, CH4N2O, the compound by which much nitrogenous body waste is excreted in the urine. a u b u c u

Solution The chemical formula for urea is CH4N2O,
MW = n(at. Wt. C) + m(at. Wt. H) + k(at. Wt. O) MW = 1(12.01 u) + 4(1.008) + 2(14.01) + 1(16.00) MW = u or rounded off u

Electrons are embedded in a sphere of positive charge.
Models of the Atom The Plum Pudding Model Electrons are embedded in a sphere of positive charge. The Nuclear Model All of the positive charge is in a tiny central nucleus with electrons outside the nucleus. This model was developed by Rutherford after his landmark experiments.

The Rutherford Experiment

Models of the Atom (continued)
Niels Bohr ( ) Models of the Atom (continued) Bohr Model or the Solar System Model Niels Bohr in 1913 introduced his model of the hydrogen atom. Electrons circle the nucleus in orbits, which are also called energy levels. An electron can “jump” from a lower energy level to a higher one upon absorbing energy, creating an excited state. The concept of energy levels accounts for the emission of distinct wavelengths of electromagnetic radiation during flame tests.

Bohr’s Orbit Model Definitions
Quantum is the smallest increment of energy, for example, in an atom emitting or absorbing radiation. Ground state is the condition of an atom in which all electrons are in their normal, lowest energy levels. Excited state is an unstable, higher energy state of an atom.

A line spectrum for hydrogen

Neon (Ne) Fig. 3-6a, p. 49 Figure 3.6: Neon.
(a) A partially evacuated tube that contains neon gas gives a reddish-orange glow when high voltage is applied. Neon (Ne) Fig. 3-6a, p. 49

Neon, a partially evacuated tube that contains neon gas gives a reddish-orange glow when high voltage is applied. Figure 3.6: Neon. (b) The line emission spectrum of neon is obtained when light from a neon source passes through a prism. The line emission spectrum of neon is obtained when light from a neon source passes through a prism. Fig. 3-6b, p. 49

Potassium burns with a violet flame
Lithium burns with a red flame Credit: Photo Researchers, Inc.

Electromagnetic Radiation
c = ln c is the speed of light l is wavelength n is frequency

As l decreases, n and E increases
Figure 3.7: The electromagnetic spectrum. Visible light (enlarged section) is but a small part of the entire spectrum. The energy of electromagnetic radiation increases from the radio wave end to the gamma ray end. The frequency of electromagnetic radiation is related to the wavelength by vλ = c where v = frequency; λ = wavelength; and c = speed of light, 3.00 x 108 meters (m)/second (s). The higher the frequency, the lower the wavelength and the larger the energy. The energy (E) of a photon (or quantum) of light is given by the expression Ephoton = hv where h is Planck’s constant ( x 10−34 J · s). It is important to understand E (for energy), wavelength, and frequency relationship: As l decreases, n and E increases As l increases, n and E decreases Fig. 3-7, p. 50

Models of the Atom (continued)
The Orbital Model Orbits are replaced with orbitals, volumes of space where the electrons can be found. The arrangement of electrons in the orbitals is the electronic configuration of an atom, which determines the chemistry of the atom.

Definitions Electrons in the highest occupied energy level are the greatest stable distance from the nucleus. These outermost electrons are known as valence electrons. Shell is a principal energy level defined by a given value of n, where n can be 1,2,3,4 etc… and is capable of holding 2n2 electrons. An orbital is a region of three-dimensional space around an atom within which there is a significant probability (usually shown as 90%) that a given electron will be found. Subshells have different energy levels (orbitals) within a given shell

Valence Electrons The valence electrons
determine the chemical properties of the elements. are the electrons in the highest energy level. are related to the group number of the element. Example: Phosphorus has 5 valence electrons. 5 valence electrons P Group 5A(15) , 8, 5

Groups and Valence Electrons
All the elements in a group have the same number of valence electrons. Example: Elements in group 2A(2) have two (2) valence electrons. Be 2, 2 Mg 2, 8, 2 Ca 2, 8, 8, 2 Sr 2, 8, 18, 8, 2

Periodic Table and Valence Electrons
Representative Elements Group Numbers H He Li Be Al C N O F Ne 2, , , , , , , ,8 Li Mg Ge Si P S Cl Ar 2,8,1 2,8,2 2,8,3 2,8,4 2,8,5 2,8,6 2,8,7 2,8,8

Learning Check State the number of valence electrons for each. A. O
1) ) 6 3) 8 B. Al 1) ) 3 3) 1 C. Cl 1) 2 2) 5 3) 7

Solution State the number of valence electrons for each. A. O 2) 6
2) 6 B. Al 2) 3 C. Cl 3) 7

Learning Check State the number of valence electrons for each.

Solution State the number of valence electrons for each. A. 2, 8, 5 5

Energy levels are spaced differently, like ladder rungs
Credit: Foto-Search.com

Atomic energy levels are like floors of a house

State transitions for hydrogen

Table 3-2, p. 52

Atomic Orbitals. Fig. 3-8, p. 54 Figure 3.8: Atomic orbitals.
Boundary surface diagrams for electron densities of 1s, 2s, 2p, 3s, 3p, and 3d orbitals. For the p orbitals, the subscript letter on the orbital notation (x, y, z) indicates the cartesian axis along which the orbital lies. Fig. 3-8, p. 54

Fig. 3-9, p. 55 Figure 3.9: Subshell filling order.
Subshells in atoms are filled in order of increasing energy, as this diagram shows. The order of filling is 1s → 2s → 2p → 3s → 3p → 4s → 3d and so on. Fig. 3-9, p. 55

The Orbital Model: Electronic Configurations

Sample energy level diagram

Table 3-3, p. 55

Figure 3.10: In this “building-up” version of the periodic table, the lightest elements are at the bottom. Electrons fill subshells from bottom to top in order of energy as the atomic number of the atom increases. The numbers across the top give the number of electrons in each subshell. The ground-state electron configurations of most elements are apparent from their positions in the table. Those that are known to differ from expectation are indicated explicitly. Fig. 3-10a, p. 56

Figure 3.10: In this “building-up” version of the periodic table, the lightest elements are at the bottom. Electrons fill subshells from bottom to top in order of energy as the atomic number of the atom increases. The numbers across the top give the number of electrons in each subshell. The ground-state electron configurations of most elements are apparent from their positions in the table. Those that are known to differ from expectation are indicated explicitly. Fig. 3-10b, p. 56

The Periodic Table Used to organize the elements by recurring chemical properties. Elements in the same vertical column of the periodic table have similar chemical properties and are said to be in the same group or family.

The Periodic Table Dmitri Mendeleev ( )

Groups and Periods On the periodic table,
elements are arranged according to similar properties. groups contain elements with similar properties in vertical columns. periods are horizontal rows of elements.

Groups and Periods Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings

Group Numbers Group Numbers
use the letter A for the representative elements (1A to 8A) and the letter B for the transition elements. also use numbers 1-18 to number the columns from left to right.

Names of Some Representative Elements
Several groups of representative elements are known by common names. Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check Identify the element described by the following.
A. Group 7A(17), Period 4 1) Br 2) Cl 3) Mn B. Group 2A(2), Period 3 1) beryllium 2) boron 3) magnesium C. Group 5A(15), Period 2 1) phosphorus 2) arsenic 3) nitrogen

Solution A. Group 7A (17), Period 4 1) Br B. Group 2A (2), Period 3
3) magnesium C. Group 5A(15), Period 2 3) nitrogen

Metals, Nonmetals, and Metalloids
The heavy zigzag line separates metals and nonmetals. Metals are located to the left. Nonmetals are located to the right. Metalloids are located along the heavy zigzag line between the metals and nonmetals. Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings

Comparing a Metal, Metalloid, and Nonmetal

Learning Check Identify each of the following elements as
1) metal 2) nonmetal ) metalloid A. sodium ____ B. chlorine ____ C. silicon ____ D. iron ____ E. carbon ____

Solution Identify each of the following elements as
1) metal 2) nonmetal ) metalloid A. sodium 1 metal B. chlorine 2 nonmetal C. silicon 3 metalloid D. iron 1 metal E. carbon 2 nonmetal

Learning Check Match the elements to the description.
A. Metals in Group 4A(14) 1) Sn, Pb ) C, Si ) C, Si, Ge, Sn B. Nonmetals in Group 5A(15) 1) As, Sb, Bi ) N, P 3) N, P, As, Sb C. Metalloids in Group 4A(14) 1) C, Si, Ge, ) Si, Ge ) Si, Ge, Sn, Pb

Solution Match the elements to the description.
A. Metals in Group 4A (14) 1) Sn, Pb B. Nonmetals in Group 5A(15) 2) N, P C. Metalloids in Group 4A(14) 2) Si, Ge

Figure 3.11: Modern periodic table of elements.
Fig. 3-11, p. 58

Table 3-4, p. 59

Carbon Gold Sulfur Three elements: sulfur (bottom) and diamond (which is carbon, top left), which are main-group nonmetals; and gold (top right), a transition metal. p. 60

The Octet Rule The noble gases of Group VIIIA do not typically form compounds with other atoms. Atoms with eight valence electrons are particularly stable, an observation called the octet rule. Atoms form bonds with other atoms to achieve a valence octet.

Electronic Configuration of Noble Gases

Lewis Dot Structures The number of valence electrons is equal to the group number for most of the main group elements. In Lewis dot structures, the chemical symbol represents the nucleus and the core electrons and dots represent the valence electrons.

Writing Electron-Dot Symbols
Electron-dot symbols for groups 1A(1) to 4A(14) use single dots. · · Na · · Mg · · Al · · C · groups 5A(15) to 7A(17) use pairs and single dots. · · · · · P · : O · · ·

Groups and Electron-Dot Symbols
In a group, all the electron-dot symbols have the same number of valence electrons (dots). Example: Atoms of elements in Group 2A(2) each have 2 valence electrons. · Be · · Mg · · Ca · · Sr · · Ba ·

Lewis Dot Structures

Learning Check A. X is the electron-dot symbol for 1) Na 2) K 3) Al
 A. X is the electron-dot symbol for 1) Na 2) K 3) Al   B.  X   is the electron-dot symbol of 1) B 2) N 3) P

Solution 1) Na 2) K  is the electron-dot symbol of
A. X is the electron-dot symbol for 1) Na 2) K   B.  X   is the electron-dot symbol of 2) N 3) P

Ionic Bonds Ionic compounds result from the loss of electrons by one atom (usually a metal) and the gain of electrons by another atom (usually a nonmetal). Ionic bonds arise from the attraction between particles with opposite charges (electrostatic forces); e.g., Na+ Cl-.

Ionic Compounds

Atomic Radius Within A Group
Atomic radius increases going down each group of representative elements. Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings

Atomic Radius Across a Period
Going across a period left to right, an increase in number of protons increases attraction for valence electrons. atomic radius decreases. Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check Select the element in each pair with the larger atomic
radius. A. Li or K B. K or Br C. P or Cl

Solution Select the element in each pair with the larger atomic
radius. A. K B. K C. P

Key Words Chemistry Matter Pure substance Mixture Element Compound
Homogeneous mixture Heterogeneous mixture States of matter Solid Liquid Gas Physical changes Chemical changes Atom Molecule Periodic table Periods Groups or Families Main group elements

Key Words (cont) Transition elements Metals Nonmetals Semimetals
Protons Neutrons Electrons Atomic number Mass number Isotopes Atomic Mass Nucleus Electromagnetic radiation Wavelength Energy level Ground state Excited state Orbital Electronic configuration Valence electrons Outer shell

Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, and electrons. All atoms.

Similar presentations

Presentation on theme: "Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, and electrons. All atoms."— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, and electrons. All atoms.

Similar presentations

Presentation on theme: "Learning Objectives: The model of atomic theory was 1st proposed by John Dalton in 1803. Atoms are composed of protons, neutrons, and electrons. All atoms."— Presentation transcript:

Similar presentations

About project

Feedback