1. Welcome to Discovery Education Player
The Atom
Welcome to Discovery Education Player

2. What is an element?
What are the subatomic parts of an atom?

3. An atom Basic unit of matter, “unable to be cut” Element
Pure substance entirely of one atom

4. What are the Subatomic Particles?
Name three and their charges?
Proton
Neutron
Electron

5. The Atom Cloud of negative Electrons charge (2 electrons) Nucleus (a)
(b)
Cloud of negative
charge (2 electrons)
Electrons

6. Who is Neils Bohr? He proposed a theory stating:
an atom is composed of a dense nucleus with electrons in its surrounding orbit
The electrons must have a certain amount of energy to orbit the nucleus.
Suggests that electrons more in a fixed manner around the nucleus.

7. Modern Atom Model Electron cloud model
Protons have a mass: 1.67 x g
Mass is so small, units atomic mass unit
(1 amu)
Atomic number: number of protons, of the same element the protons must be the same
Electrons: are equal to but have an opposite charge to that of a proton
Less mass 1/1836 amu
Mass number: sum of the protons and neutrons

8. Atomic Structure 15 7N Mass number = protons plus neutrons
If mass number is 15, how many protons do you have if you have 8 neutrons?
Atomic number = number of protons
* If the atom is neutral the protons and electrons are equal!
If the mass number is 15 and there is no charge and the atomic number is 7 how many electrons and neutrons do you have?

9. Atomic Structure Continued!!
Atomic Number
The number of protons in the nucleus of an atom
Determines which element
Mass Number
The number of nucleons (protons + neutrons)
If you don’t know the mass number you can round off the atomic mass for that element
# neutrons = mass # - atomic #
The atomic number cannot change. Mass number can.

10. Element
Atomic Number
Atomic Mass
Mass #
Protons
Neutrons
Electrons

11. Element
Atomic #
Atomic Mass
Mass Number
Protons
Neutrons
Electrons

12. Each electron in an atom has its own distinct amount of energy.
When electrons are in their lowest energy state, it is called the ground state
The ground state for Na is

13. Tom Lehrer's "The Elements"
Tom Lehrer's "The Elements". A Flash animation by Mike Stanfill, Private Hand

14. II. Periodic Table

15. elements: Periodic Table are arranged in increasing atomic number.
Placement or location of elements on the Periodic Table indicates the physical and chemical properties of that element.
Number of protons in an atom (atomic number) identifies the element
Atomic mass: found on the Periodic Table of the Elements

16. Classifying Elements Nonmetals on the right Metals on the left
metalloids or semimetals (B, Si, Ge, As, Sb, Te),
noble gases
Nonmetals on the right
Metals on the left
Metalloids semimetals

17. Average atomic mass of an element
Average atomic mass of an element the weighted average of the masses of its naturally occurring isotopes
Isotope
Mass
Abundance
Calculation
12C 12
98.89%
12 x =
13C 13
1.108%
13 x =
Atomic Mass (weighted average)
12.01 amu

18. Isotopes C-12 isotope C-13 isotope C-14radioactive
Isotope: identified by the sum of the protons and neutrons in an atom = (mass number)
Isotope: atom of the same element having same number of protons but different number of neutrons
14C, carbon-14, C-14
C-12 isotope C-13 isotope C-14radioactive

19. Density=mass/volume
A physical property is one which does not change the identity of the substance when tested.

20. Differentiation of Elements
physical properties differentiate elements by their Physical properties
ex: density, conductivity, malleability, solubility, and hardness, differ
Elements can be differentiated by chemical properties too.
Chemical properties describe how an element behaves during a chemical reaction.
When testing a chemical property, the substance may change into another substance.

21. Buckminsterfullerene
Some elements exist in two or more forms in the same phase. These forms differ in their molecular or crystal structure, and hence in their properties. These are called allotropes.
Allotropes of oxygen
Allotropes of carbon
Oxygen ( O2 )
Graphite
Ozone ( O3 )
Diamond
Buckminsterfullerene

22. allotropes Some elements exist in two or more forms of the same phase.
They differ in molecular or crystal structure, and in properties.

23. Comparing the physical properties of metals and nonmetals
Many different colors
Sulfur – yellow
Chlorine – green
Bromine – orange
Iodine - purple
Many different states (phases)
H, N, O – gas
Br – liquid
S, C, I – solid
Poor conductors of heat and electricity (except carbon)
Brittle – breaks when hit
Silvery gray color except copper and gold
Solid at room temperature except mercury
Good conductors of heat and electricity
Malleable – can be hammered into shapes (thin sheets)
Ductile – can be pulled into wires

24. All elements are solid at room temperature except for the following:
Liquids
Mercury (Hg) - the only liquid metal at room temperature
Bromine (Br) - the only liquid nonmetal at room temperature
Gases
Hydrogen (H)
Oxygen (O)
Nitrogen (N)
Fluorine (F)
Chlorine (Cl)
All of group 18 (noble gases)
Helium (He), Neon (Ne) Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn)

25. For Groups 1, 2, and on the Periodic Table, elements within the same group have the same number of valence electrons (helium is an exception) and therefore similar chemical properties.

26. Group numbers and family names
Group 1 Alkali Metals
Very reactive metals, always found as compounds in nature
1 valence electron - lose 1 electron to form +1 ions
Group 2 Alkaline Earth Metals
Reactive metals, always found as compounds in nature
2 valence electrons - lose 2 electron to form +2 ions
Group 17 Halogens
Reactive nonmetals
7 valence electrons - gain 1 electron to form –1 ions
Groups 18 Noble Gases
Not reactive – do not form ions
Filled, stable valence shell (8 electrons except He which has 2)

27. The succession of elements within the same group demonstrates characteristic trends: differences in atomic radius, ionic radius, electronegativity, first ionization energy, metallic/nonmetallic properties.
Going down a group, there are more shells separating the nucleus from the valence electrons

28. Reference Table S

29. Trends in Atomic Radius
Atomic Radius – half the distance between two nuclei
Going down a group, the atomic radius increases because there are more principal energy levels (shells)
Going across a period, the atomic radius decreases because there are more protons pulling the valence shell closer

30. Atomic Radius

31. The succession of elements across the same period demonstrates characteristic trends: differences in atomic radius, ionic radius, electronegativity, first ionization energy, metallic/nonmetallic properties.
Going across a period, there are more protons pulling on the valence electrons

32. Forming Ions – making atoms happy
Atoms gain or lose electrons to complete their outer shell
A noble gas configuration
A complete octet
8 electrons
Metals lose electrons to form positive (+) ions
Nonmetals gain electrons to form negative (-) ions
Ionic Radius
A negative ion is always larger than its original atom.
A positive ion is always smaller than its original atom.

33. Ionic Radius in Metals Sodium (Na) is a metal
Electron configuration 2-8-1
(11 protons and 11 electrons)
Loses 1 electron in its valence shell
A sodium atom becomes a sodium ion
Na+
2-8 (10 electrons but 11 protons)
Same electron configuration as a noble gas (Ne) but has more protons. Electrons are pulled in much closer so the radius decreases.
2+ ions are even smaller than + ions

34. Ionic Radius in Nonmetals
Notice-name of negative ions end in IDE
Chlorine (Cl) is a nonmetal
Electron configuration 2-8-7
(17 protons and 17 electrons)
Gains 1 electron in its valence shell
A chlorine atom becomes a chloride ion
Cl-
(18 electrons but only 17 protons)
Same electron configuration as a noble gas (Ar) but has fewer protons. Electrons repel each other and the radius increases.
2- ions are even larger than – ions