Chem 110 Test 1 Chapter 3 Review

Electron energy levels

Regions surrounding the nucleus where electrons are found. Each energy level is identified by a principal quantum number (n).

• n=1, 2e-

• n=2, 8e-

• n=3, 18e-

• n=4, 32e-

Max number in energy level: use 2n², where n is energy level number

As n increases, electron energy generally increases and electrons occupy regions farther from the nucleus

Determining the locations of electrons

The number of electrons equals the atomic number (num of protons)

Ex carbon: n=1, 2e-, n=2, 4e-

oxygen: n=1, 2e-, n=2, 6e-

sodium: n=1, 2e-, n=2, 8e-, n=3, 1e-

Valence electrons

Electrons in the outermost occupied energy level of an atom that are involved in chemical bonding.

Na=1

O=6

Cl=7

Ne=8

Octet rule

Atoms tend to gain, lose, or share electrons to achieve 8 electrons in their outermost energy level.

• Atoms tend to gain, lose, or share electrons to achieve 8 electrons in their outermost energy level.

• Noble gases already have full valence shells, making them relatively unreactive

• Helium's first energy level is full with only 2 electrons.

• Sodium achieves a stable electron configuration by losing 1 electron to form Na+, achieving the electron config of neon

• Cl achieves table electron config by gaining 1 e- to form cl-, achieving the electron config of argon

Ion

An atom or group of atoms that has gained or lost electrons and carries an electrical charge.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

What happens when an atom loses electrons?

It becomes a positively charged cation.

What happens when an atom gains electrons?

It becomes a negatively charged anion.

Metals form _ ions

positive ions (cations)

Nonmetals form

negative ions (anions)

Isoelectrionic

Atoms or ions that have the same number of electrons and the same electron configuration.

Cl- and Ar: both have 18 e- and same electronic config

Na+ and Ne, both have 10 e- and same e- configuration

How can you predict the ion formed by a neutral element?

Determine its valence electrons and whether it will gain or lose electrons to achieve a stable configuration.

Like group 1A , +1

Polyatomic ion

A group of two or more covalently bonded atoms that carries an overall electrical charge.

(NO3-), -1

Predicting Ionic Compound Formulas (criss-cross method)

A method for writing ionic formulas by using the magnitude of each ion's charge as the subscript of the opposite ion.

What is the formula for aluminum oxide?

• Al2O3

Reverse Criss-Cross Method

A method used to determine ion charges from an ionic compound's formula.

What charge does iron have in FeCl₂?

• +2 because two chloride ions each have a −1 charge.

Naming Ionic Compounds

Name the cation first, followed by the anion.

What is (NH₄)₂SO₄ called?

• Ammonium sulfate.

What is CaCO₃ called?

• Calcium carbonate.

Ionic v Covalent compounds

What is the main difference between ionic and covalent bonding?

• Ionic bonding involves attraction between oppositely charged ions, while covalent bonding involves sharing electrons.

Ionic: metal and nonmetal

Covalent: two or more nonmetals

Is CH₄ ionic or covalent?

• Cov

Is CaO ionic or covalent?

• Ionic