Atoms & Elements

What is an atom? An atom is the smallest particle of an element that retains its identity in a chemical reaction. Word origin: atom comes from the Greek word atomos meaning “ indivisible”

Elements & Compounds What would atoms of an element, mixture and compound look like at a microscopic level?

Subatomic Particles The parts that make up an atom! protons neutrons electrons electron proton nucleus neutron

Subatomic Particles Electrons Protons Neutrons Found in the nucleus Identifies the element #of protons = specific element Responsible for chemical and physical properties Spin around in set regions outside of nucleus Most important in chemical reactions Farthest electron away from nucleus determines how atoms chemical to combine to one another. Found in the nucleus Plays no role in chemical behavior Purpose: to put space between protons

Subatomic Particles How big is an atom? Name Symbol Charge Relative Mass Proton p+ +1 1 Neutron no Electron e- -1 0 (1/1840) How big is an atom? Imagine the nucleus is the size of a marble located in the middle of the football field, the electron would be in the classroom the size of a period!

Periodic Table Greatest Cheat Sheet Ever!

Periodic Table Categories: Rows: periods Columns: groups or families Metals Nonmetals Metalloids (B, Si, Ge, As, Sb, Te, At) Rows: periods 7 periods Columns: groups or families 18 Groups 1A: Alkali Metals 2A: Alkaline Earth Metals 7A: Halogens 8A: Noble gases B Groups: Transition and Inner Transition Metals

Si Periodic Table 14 Silicon 28.086 Atomic Number Symbol Element name Atomic Mass

Si Important Numbers Atomic Number 14 Silicon has 14 protons Counts the number of protons in an atom within the nucleus Atomic Number = # of protons 14 Si Silicon has 14 protons

Atomic Number A. Nitrogen B. Potassium C. Neon State the number of protons for atoms of each of the following: A. Nitrogen B. Potassium C. Neon

Atomic Number A. Nitrogen B. Potassium C. Neon 7 protons 19 protons State the number of protons for atoms of each of the following: A. Nitrogen 7 protons B. Potassium 19 protons C. Neon 10 protons

Number of Electrons An atom is neutral The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons Remember: proton = +1 electron = -1

Number of Electrons 14 Si 14 electrons 14 protons -14 +14 = 0 neutral

Si Important Numbers Mass Number 14 Atomic Mass Silicon 28.086 Counts the number of protons and neutrons in an atom OR Determined by: the whole number closest to the Atomic Mass

Si 28 14 Mass Number silicon-28 Show the mass number and atomic number Atomic Symbols Show the mass number and atomic number Give the symbol of the element Mass Number 28 14 Si silicon-28 Atomic Number

Determine the Mass Numbers 4 Be 9.0122 27 Co 58.933 10 Ne 20.179 9 59 20

Write the Symbol and Name for each 4 Be 9.0122 27 Co 58.933 10 Ne 20.179 Be 9 4 59 27 Co 20 10 Ne beryllium-9 cobalt-59 neon-20

Mass Number O P Zn The total number of particles in the nucleus # of protons + # of neutrons To determine the number of neutrons Mass number – Atomic number = # of neutrons O 16 8 31 15 65 30 #p #n #e P Zn 8p+ 30p+ 15p+ 8no 35no 16no 8e- 30e- 15e-

Isotopes The atomic number identifies the element, but an element may have atoms with several different mass numbers. Most elements consist of several different isotopes Same number of protons , Different number of neutrons 35 17 Cl 37 17 Cl chlorine-35 chlorine-37

Isotopes of Hydrogen Naturally occurring hydrogen consists of 3 isotopes, protium (H-1), deuterium (H-2), and tritium (H-3). State the number of protons, neutrons, and electrons. 1 2 3 #p #n #e H H H 1 1 1 1 2 1 1 1

An atom of Calcium (Ca-40) A. Number of protons B. number of neutrons C. What is the mass number of a calcium isotope with 19 neutrons?

Atomic Mass This is NOT a whole number A given element can have atoms with several different mass numbers. Average mass of the atoms with all possible mass numbers We will calculate later 

Write the atomic symbol A. 11p+, 12no, 11e- B. 17p+, 20no, 17e- C. 47p+, 60no, 47e-

Write the atomic symbol 23 11 Na A. 11p+, 12no, 11e- B. 17p+, 20no, 17e- C. 47p+, 60no, 47e- 37 17 Cl 107 47 Ag

Ions Na1+ Cl1- Atoms with a charge (positive or negative) Remember atoms are neutral, therefore if an atom has a charge we call it an ion. Ions- Atoms which gain or lose an electron atom ion #p 11 11 #e 11 10 #p 17 17 #e 17 18 Why do the electrons change? Na1+ Cl1-

Why? If protons change…new______?________ If neutrons change…new______?______ If electrons change….new _____?______

Why? If protons change…new element If neutrons change…new isotope If electrons change….new ion

Ions atom ion #p 12 12 #e 12 10 #p 8 8 #e 8 10 Mg 2+ O 2-

Complete Atomic Symbol combines isotopes and ions 27 13 Al 3+ What does each represent? How many of what subatomic particles does each represent?

Complete Atomic Symbol combines isotopes and ions 27 13 Al 3+ Ionic charge Mass number Atomic number 14no 13p+ 10e-

How many protons, neutrons, & electrons? 65 30 14 7 32 15 N3- Zn2+ P3- 30p+ 35no 28e- 7p+ 7no 10e- 15p+ 17no 18e-

Atomic Mass Coming back to this… Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom. So we involved all the different forms of ATOMS of an element (ions not an issue here) and how frequent they are

Average Atomic Mass cont. To find the Average Atomic Mass (generally referred to as the atomic mass of an element) we need to use two things The mass of the isotope Multiplied by its frequency Then we add all the forms up.

Example of Average Atomic Mass Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5 = 26.4 100 35.5 37 x 24.5 = 9.07 Add Us Up

Rubidium has two common isotopes, Rb-85 and Rb-87 Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of Rb-85 is 72.2% and the abundance of Rb-87 is 27.8%, what is the average atomic mass or rubidium?