Chemical Bonding

Question 1

What are the three types of bonding?

Answer 1

Ionic bond: occurs between metals and non-metals

Covalent bond: occurs between two non-metal atoms

Metallic bond: occurs between atoms in a metal

Question 2

How are ionic bonds formed?

Answer 2

When a metal and a non-metal react an ionic compound is formed.

Question 3

What are the charges of ions

Answer 3

Metals lose electrons to form positive ions while non-metals gain electrons to form negative ions

Question 4

How are covalent bonds formed?

Answer 4

When two non-metal elements react a covalent compound is formed

Question 5

How do co-ordinate bonds form?

Answer 5

For a co-ordinate bond to form, one atom needs to have a lone pair of electrons.
A second atom/ion must have a vacant orbital
The lone pair donates its electrons into the vacant orbital and his results in a co-ordinate bond being formed

Question 6

How are metallic bonds formed

Answer 6

Metal atoms in a regular arrangement form a metallic lattice. They usually have a small number of electrons on the highest energy level. When they are close together the electrons become delocalised and are no longer associated with one particular atom. This creates a lattice of positively charged ions in a sea of delocalised electrons. There is an attraction between the positive ions and sea of electrons throughout the lattice. This attraction is called a metallic bond

Question 7

What does the strength of a metallic bond depend on?

Answer 7

1) the charge on the metal ions

2) the size of the metal ions

Question 8

How does the charge on the metal ions affect the strength of the metallic bond?

Answer 8

The greater the charge on the metal ions, the greater the attraction between the ions and delocalised electrons, and the stronger the metallic bonds. A higher melting point is evidence of stronger bonds in a substance.

Question 9

How does the size of the metal ions affect the strength of metallic bonds?

Answer 9

The smaller the metal ion, the closer the positive nucleus is to the delocalised electrons. This means there is a greater attraction between the two, which creates a stranger metallic bond.

Question 10

What is electronegativity

Answer 10

In a covalent bond between two different elements, the electro. Density is not shared equally.

This is because different elements have differing abilities to attract the bonding electron pair. This ability is called an element’s electronegativity.

Question 11

What does the electronegativity of an element depend on?

Answer 11

1) Atomic radius

2) Number of unshielded protons

Question 12

How does the Atomic radius affect the electronegativity of an element?

Answer 12

As radius of an atom increases, bonding pair of electrons become further from the nucleus. They are therefore less attracted to the positive charge of the nucleus, resulting in a lower electronegativity.

Question 13

How does the number of unshielded prints affect the electronegativity of an element

Answer 13

The greater he number of pronto s in a nucleus, the greater the attraction to the electrons in the covalent bond, resulting in higher electronegativity. However, full energy levels of electrons shield the electrons in the bond from the increased attraction of the greater nuclear charge, thus reducing electronegativity.

Question 14

What are non-polar bonds?

Answer 14

The electronegativity of both atoms in Covent bond is identical, the electrons in the bond will be equally attracted to both of them.

This results in. Symmetrical distribution. Of electron density around the two atoms.

Elements will always be non-polar because the electronegativity is the same.

Question 15

Why do polar bonds occur?

Answer 15

When a covalent bond is formed between two different atoms a polar bond may result.

If the electronegativity are different they will have different abilities to attract he electrons in the bond.

Question 16

What happens in a polar bond?

Answer 16

An asymmetrical distribution of electron density results because one atom attracts the electrons more strongly. This creates an imbalance in the charges in the bond called a dipole.

Question 17

What happens to the greater density of polar bonds?

Answer 17

The atom surrounded by the greater share of he electron density has a slight negative charge

The atom with a lesser share surrounding it has a slight positive charge

Question 18

What effect does electronegativity have on polarisation?

Answer 18

The greater the electronegativity difference between two atoms in a bond the greater the polarisation of the bond.

Question 19

Is covalent bonds more polar or non-polar? Why?

Answer 19

Less polar bonds have more covalent character and more polar bonds have more ionic character. The more electronegative atom attracts the electrons in the bond enough to ionise the other atom.

Question 20

What are polar molecules?

Answer 20

Molecules containing polar bonds are not always polar:

Polar molecules: If the polar bonds are arranged asymmetrically, the partial charges do not cancel out and the molecule is polar

Question 21

What is a non-polar bond?

Answer 21

If the polar bonds are arranged symmetrically, the partial charged cancel out and the molecule is non-polar

Question 22

What are intermolecular forces?

Answer 22

The forces of attraction between the molecules in simple covalent substances.

Question 23

What are the three main types of intermolecular forces?

Answer 23

1) Van Der Waals forces
2) Permanent dipole-dipole forces
3) hydrogen bonds

Question 24

What are Van der Waals forces?

Answer 24

Electrons always move, this means that even non-polar bonds occasionally have a temporary dipole in the molecule where one end will be slightly more positive and the other negative. This can cause a dipole in surrounding molecules as well causing the slightly negative side of one molecule to be attracted to be slightly positive side of another and hence a weak force of attraction between small charges occurs.

Question 25

How does he molecular size affect the strength of Van der Waals forces?

Answer 25

Atomic radius increases down the group, so the outer electrons become further from the nucleus. They are attracted less strongly by the nucleus and so temporary dipoles are easier to induce.

Question 26

How do the points of contact affect the strength of Van der Waals forces?

Answer 26

Straight chain alkaline can pack closer together than branches alkanes, creating more points of contact between molecules. This results in stronger Van der Waals forces.

Question 27

What are permanent dipole-dipole forces?

Answer 27

When two atoms in a molecule have substantially different electronegativity: one atom attracts electrons more that the other

Question 28

What are hydrogen bonds

Answer 28

When hydrogen bonds to nitrogen, oxygen or fluorine a larger dipole occurs than in other polar bonds. This is because these atoms are highly electronegative due to heir high nuclear charge and small size. So when they bond to hydrogen the electrons are withdrawn from H making it slightly positive. H very small = positive charge more concentrated = easier to link with other molecules. Therefore they permanent dipole-dipole forces on steroids

Question 29

The boiling point of hydrogen fluoride is much higher than hydrogen halides, due to fluorines high electronegativity. What does this mean.

Answer 29

Hydrogen bonding between molecules of hydrogen fluoride is much stronger than the permanent dipole-dipole forces between molecules of other hydrogen halides. More energy is therefore required to separate the molecules of hydrogen fluoride.

Question 30

What are cations and anions?

Answer 30

Cations - positively charged ions

Anions - negatively charged ions