Atoms, Ions and Molecules – Intro
Answer Key
1. The atom is the basic unit of matter. It is made up of three components the protons, electrons and neutrons.
2. Protons are located in the nucleus and have a positive charge. The number of protons defines the element. When you change the number of protons you create a new element.
3. Electrons are located in the orbitals and have a negative charge. The electrons (primarily valence electrons) define the chemical properties of the element. When you change the number of electrons you create an ion.
4. Neutrons are located in the nucleus and have a neutral charge. When you change the of neutrons you create an isotope.
5. The elements are organized in the periodic table. Elements in the same column (group) have similar reactivities.
a. Groups names to know
i. Group 1A – Alkali Metals
ii. Group 2A – Alkaline Earth Metals
iii. Group 7A – Halogens
iv. Group 8A – Noble Gases
6. How to determine the
a. Atomic Number ( Z ) = Number of protons
b. Mass Number ( A ) = Number of protons + Number of neutrons
7. True or False
a. Atomic Mass is just another name for the mass number
False. The atomic mass is a weighted average of all isotopes of a particular element. The mass number is associated with a particular isotope.
8. In a neutral atom,
a. The number of protons, electrons and neutrons are all equal.
b. The number of protons and neutrons are equal. The electron count can be different.
c. The number of neutrons and electrons are equal. The proton count can be different.
d. The number of protons and electrons are equal. The neutron count can be different.
9. 12C, 13C, and 14C are isotopes of each other.
10. In a cation there is an overall positive charge.
In an anion there is an overall negative charge.
11. What elements on the period table tend to not form ions? Why?
Noble gases. They have aperfect electron configuration. All orbitals are filled.
a. What is ion most commonly formed by
i. Alkali Metals – 1+ (one electron is lost)
ii. Alkaline Earth Metals – 2+ (two electrons are lost)
iii. Group 3A – 3+ (three electrons are lost)
iv. Group 5A – 3- (there electrons are gained)
v. Group 6A – 2- (two electrons are gained)
vi. Halogens – 1- (one electron is gained)
The configurations that are obtained by the loss or gain of electrons gives the very favorable configuration of the nearest noble gas..
12. One of the most important characteristics of atoms is their ability to form bonds. There are 2 main categories of bond
a. Covalent Bonds
In this case the atoms are held together by shared pairs of electrons.
This type of bond occurs between 2 nonmetals.
b. Ionic Bonds
In this case the atoms are held together by attractive forces between positive and negative charges.
This type of bond occurs between a metal and nonmetal.
13. There are a set of elements that are naturally found as diatomic molecules; they are
H2, O2, N2, F2, Cl2, Br2, I2
Some people remember this by
Have No Fear Of Ice Cold Beer
14. Rules for Nomenclature of Binary (2 types of elements) Compounds
a. Ionic containing metals with only one possible ion
i. Metal cation named first using it’s proper name
ii. Nonmetal anion named using element root name with “-ide” suffix.
1. Name the following
a. CaCl2
Metal = Calcium
Nonmetal = Chlor – ide
Full name = Calcium chloride
b. Mg3N2
Metal = Magnesium
Nonmetal = Nitr - ide
Full name = Magnesium nitride
b. Ionic containing metals that can form more than one type of ion
i. Metal cation named first using it’s proper name and charge on ion indicated by roman numerals.
ii. Nonmetal anion named using element root name with “-ide” suffix.
1. Name the following
a. CuF
Metal = Copper (I)
Nonmetal = Fluor - ide
Full name = Copper (I) fluoride
b. Hg2O
Metal = Mercury (I)
Nonmetal = Ox - ide
Full name = Mercury (1) oxide
c. Covalent Compounds (XaYb)
i. Indicate “a” using prefix (see naming information sheet) and attach to “X” element name. (If a=1 simply use element name – do not use prefix mono-)
ii. Indicate “b” using prefix (see naming information sheet) and attach to “Y” element root name with “-ide” suffix.
1. Name the following
a. N2O4
First element = Dinitrogen
Second Element = Tetroxide
Full name = Dinitrogen tetroxide
b. H2O
Bit of a trick question in that we refer to this compound almost exclusively as water. Now and then a teacher will use dihydrogen monoxide to throw you a bit.
15. What is a polyatomic ion?
A covalently bonded molecule with an overall charge.
a. Name the following
i. CaSO3
Cation = Calcium
Anion = Sulfite
Full name = Calcium sulfite
ii. NH4Cl
Cation = Ammonium
Anion = Chloride
Full name = Ammonium chloride
16. How do you identify an acid?
For now, an acid is identified as a compound that has one or more hydrogens attached to an anion. The anion is what we derive the name from.
17. Rules for Nomenclature of an acid
a. Name the Following
i. HC2H3O2
anion = acetate
acid name = Acetic acid
ii. HCl
anion = chloride
acid name = hydrochloric acid