Chapter 3 Chemical Foundations: Elements, Atoms, and Ions Atoms, Ions and Isotopes

Learning Targets You will learn about atoms, ions and isotopes.

Symbols to be familiar with: The atom Symbols to be familiar with: Protons = p+ Neutrons = n0 Electrons = e- Atoms are always neutral Neutral = Same number of protons and electrons

The symbol for an atom A Z A = the mass number (# p+ + n0) X Z A = the mass number (# p+ + n0) X = symbol of element Z = the atomic number (number of protons)

Funnies  Two molecules are walking down the street; one bumps into the other and says: "Oh, my fault, you okay?” The Second Molecule says: "No, I'm not ok, I've lost an electron!" So the first molecule says: "Are you sure" the second molecule answers, "I'm positive!"

Calculating mass number 1 equation rearranged: A = Z + neutrons Mass Number = # of protons + # neutrons OR A – neutrons = Z Mass number – neutrons = # protons A – Z = neutrons Mass number - # protons = # neutrons

Isotopes Isotopes are atoms that have the same number of protons, different number of neutrons Often represented as: element name – mass #. (Example: carbon – 14)

Practice Give the number of protons, neutrons and electrons in the atom symbolized by 201 Hg 80 Give the symbol to represent the following information: The cesium atom with a mass number of 132

Try on your own Give the number of protons, neutrons and electrons in the atom symbolized by 90 Sr 38 Strontium-90 occurs in fallout from nuclear testing. It can accumulate in bone marrow and may cause leukemia and bone cancer. Give the symbol to represent the following information: The iron atom with a mass number of 56

Ions Ions are atoms with a charge cations (positively charged ion) anions (negatively charged ion) Ions have a charge because they are gaining or losing electrons from their neutral atom Symbol is element symbol with the ion charge as a superscript (Example: Ca2+) Usually formed when metals combine with nonmetals

Ions that certain groups form on the periodic table

Ions that certain groups form on the periodic table Groups have similar characteristics – one being how many electrons are lost or gained from the neutral atom Ions have unequal numbers of protons and electrons. Different from atoms because numbers are equal. Group 1: 1+ Group 2: 2 + Group 3 or 13: 3 + (there are exceptions) Group 4 or 14: gives or takes electrons Group 5 or 15: 3- (there are exceptions) Group 6 or 16: 2- Group 7 or 17: 1- **know these charges and put on periodic table

Examples For each of the following ions, indicate the total number of protons and electrons in the ion (#46 in your book) A. Co2+ E. S2- B. Co3+ F. Sr2+ C. Cl- G. Al3+ D. K+ H. P3-

Examples-Answers A. 27 p, 25 e B. 27 p, 24 e C. 17 p, 18 e D. 19 p, 18, e E. 16 p, 18 e F. 38 p, 36 e G. 13 p, 10 e H. 15 p, 18 e

Homework Atomic Structure Worksheet DUE MONDAY