Bonding, Shapes of Molecules, Intermolecular Forces and Chemical Structures

Question 0

What is a giant ionic lattice?

Answer 0

A three-dimensional structure of oppositely-charged ions, held together by strong ionic bonds.

Question 1

What is ionic bonding?

Answer 1

The electrostatic attraction between oppositely-charged ions.

Question 2

What is a group?

Answer 2

A vertical column in the Periodic Table. Elements in the same group have similar chemical properties and their atoms have the same number of outer-shell electrons.

Question 3

What is the formula of an ammonium ion?

Answer 3

NH₄⁺

Question 4

What is the formula of a hydroxide ion?

Answer 4

OH⁻

Question 5

What is the formula of a nitrate ion?

Answer 5

NO₃⁻

Question 6

What is the formula of a nitrite ion?

Answer 6

NO₂⁻

Question 7

What is formula of a hydrogencarbonate ion?

Answer 7

HCO₃⁻

Question 8

What is formula of a carbonate ion?

Answer 8

CO₃²⁻

Question 9

What is the formula of a sulfate ion?

Answer 9

SO₄²⁻

Question 10

What is formula of a sulfite ion?

Answer 10

SO₃²⁻

Question 11

What is formula of a dichromate ion?

Answer 11

Cr₂O₇²⁻

Question 12

What is the formula of a phosphate ion?

Answer 12

PO₄³⁻

Question 13

What is a covalent bond?

Answer 13

A bond formed by a shared pair of electrons.

Question 14

What is a lone pair?

Answer 14

An outer-shell pair of electrons that is not involved in chemical bonding.

Question 15

What is a dative covalent bond?

Answer 15

A shared pair of electrons which has been provided by one of the bonding atoms only. It is also known as a coordinate bond.

Question 16

What is the shape of a simple molecule determined by?

Answer 16

The repulsion between electron pairs surrounding a central atom. Lone pairs of electrons repel more than bonded pairs.

Question 17

What is a tetrahedral molecule? Give an example.

Answer 17

A molecule with bond angles of 109.5°, with four bonded pairs in total, i.e. CH₄.

Question 18

What is a trigonal planar molecule? Give an example.

Answer 18

A molecule with bond angles of 120°, with three bonded pairs in total, i.e. BF₃.

Question 19

What is a pyramidal molecule? Give an example.

Answer 19

A molecule with bond angles of 107°, with three bonded pairs and one lone pair in total, i.e. NH₃.

Question 20

What is a non-linear molecule? Give an example.

Answer 20

A molecule with bond angles of 104.5°, with two bonded pairs and two lone pairs in total, i.e. H₂O.

Question 21

What is an octahedral molecule? Give an example.

Answer 21

A molecule with bond angles of 90°, with six bonded pairs, i.e. SF₆.

Question 22

What is a linear molecule? Give an example.

Answer 22

A molecule with bond angles of 180°, with two bonded regions in total, i.e. CO₂.

Question 23

How does a lone pair affect the bond angle?

Answer 23

It decreases it by 2.5°.

Question 24

What is electronegativity?

Answer 24

A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.

Question 25

What is a permanent dipole?

Answer 25

A small charge difference across a bond that results from a difference in the electronegativities of the bonded atoms.

Question 26

What is a polar covalent bond?

Answer 26

A bond that has a permanent dipole.

Question 27

What is a polar molecule?

Answer 27

A molecule that has an overall dipole, when you take into account any dipoles across the bonds.

Question 28

What is the trend of electronegativities across a period and down a group? Explain this.

Answer 28

Electronegativity increases from left to right across a period and decreases down a group. This is because the electron shielding increases down a group and the nuclear charge increases from left to right across a period.

Question 29

What is an intermolecular force?

Answer 29

An attractive force between neighbouring molecules.

Question 30

What is a permanent dipole-dipole force?

Answer 30

A weak attractive force between permanent dipoles in neighbouring polar molecules.

Question 31

What are van der Waals’ forces?

Answer 31

Attractive forces between induced dipoles neighbouring molecules.

Question 32

What are the relative bond strengths of ionic bonds, covalent bonds, hydrogen bonds, dipole-dipole forces and van der Waals’ forces?

Answer 32

Ionic bonds: 1000
Covalent bonds: 1000
Hydrogen bonds: 50
Dipole-dipole forces: 10
Van der Waals' forces: 1

Question 33

Do the van der Waals’ forces increase or decrease down Group 0? Why? What property demonstrates this?

Answer 33

They increase, because the electrons increase. This increases the boiling points down the group.

Question 34

What is a hydrogen bond?

Answer 34

A strong dipole-dipole attraction between an electron-deficient hydrogen atom on one molecule and a lone pair of electrons on a highly electronegative atom (N, O or F) on a different molecule.

Question 35

Explain the density of ice compared with water.

Answer 35

Ice is less dense than water, because ice has an open lattice with hydrogen bonds holding the water molecules apart, but when ice melts the rigid hydrogen bonds break, allowing the water molecules to move closer together.

Question 36

Explain the melting and boiling points of water.

Answer 36

It has relatively high melting and boiling points, because there are relatively strong hydrogen bonds between molecules, which have to be overcome on top of the van der Waals’ forces to melt or boil water.

Question 37

What is metallic bonding?

Answer 37

The electrostatic attraction between positive metal ions and delocalised electrons.

Question 38

What is a giant metallic lattice?

Answer 38

A three-dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds.

Question 39

What is a simple molecular lattice?

Answer 39

A three-dimensional structure of molecules, bonded together by weak intermolecular forces.

Question 40

What is a giant covalent lattice?

Answer 40

A three-dimensional structure of atoms, bonded together by strong covalent bonds.