Module 7 (2025) Covalent Bonding and Intermolecular Forces

Number of Valence electrons in a group 13 elements

3

Number of Valence electrons in a group 14 elements

4

Number of Valence electrons in a group 15 elements

5

Number of Valence electrons in a group 16 elements

6

Number of Valence electrons in a group 17 elements

7

Number of Valence electrons in a group 18 elements

2 for helium , 8 for the others

Why are group 18 electrons nonreactive?

They have full valence shells

Electronegativity

A measure of the ability of an atom to attract electrons

Elements with higher electronegativity

Form negative ions or covalent bonds

Nonmetals

elements with relatively high electronegativity

properties of ionic compounds

Form crystal lattices, conduct electricity in solution, and have high melting and boiling points.

properties of covalent compounds

low melting point, low boiling point, never conducts electricity

covalent bonding

sharing of electrons pairs between atoms

octet rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons

octet rule exceptions

hydrogen and helium have a full shell with only 2 electrons

Lewis Dot Model

lewis' method places dots around the elements symbol to represent the number of valence electrons

lewis dot model of a compound

shows how the atoms in the compound share electrons

each line is two electrons

lone pairs are dots

Lone pairs

pairs of valence electrons that are not involved in covalent bond formation

single bond

a covalent bond in which two atoms share one pair of electrons

double bond

A covalent bond formed when atoms share two pairs of electrons

triple bond

a covalent bond in which two atoms share three pairs of electrons

Predicting whether a bond is ionic or covalent

-big differences in electronegativity are ionic (example: metal and nonmetal)

-small differences in electronegativity are covalent (example: nonmetal and nonmetal)

shell

-location of the electrons that fill the principal energy level of an atom

- increasing number of shells generally increases the distance of the electrons in the shell from the nucleus

number of covalent bond made by a nonmetal

equals the number of spaces in the valence shell that can be filled.

For example: oxygen has 6 valence electrons, so oxygen can make 2 bonds

Covalent Bonding Pattern of Oxygen

2 single bonds or 1 double bond

Covalent bonding pattern of fluorine

1 single bond

covalent bonding pattern of nitrogen

3 bonds total

- 3 single bonds or 1 single and 1 double or 1 triple bond

covalent bonding pattern of carbon

four bonds total

-4 single bonds, 2 single and 1 double, 2 double bonds, or 1 single and 1 triple bond.

covalent bonding pattern of hydrogen

one single bond

Principle Element

Element in the second period of the periodic table

-all elements in the group have the same chemistry because they have the same number of valence electrons

Dipole

created by equal but opposite charges that are separated by a short distance

hydrogen bond

Attraction between a slightly positive hydrogen atom and a slightly negative atom in another molecule. The other atom is usually oxygen or nitrogen.

dipole-dipole forces

attractions between oppositely charged regions of polar molecules

polar molecule

molecule with an unequal distribution of charge, resulting in the molecule having a positive end and a negative end

polar bond

a covalent bond in which electrons are shared unequally

intramolecular force

forces that hold atoms and ions together in molecules and compounds (covalent or ionic bonding)

intermolecular force

forces of attraction between molecules (hydrogen bonds, dipole-dipole interactions, dispersion forces)

dispersion forces

attractions between molecules caused by the electron motion on one molecule affecting the electron motion on the other through electrical forces; these are the weakest interactions between molecules

Van der Waal forces are

dispersion forces

Nonpolar molecule

molecule that shares electrons equally and does not have oppositely charged ends