Atomic Structure and Bonding

Question 1

What are the three components of an atom?

Answer 1

Protons, neutrons and electrons.

Question 2

What is a proton?

Answer 2

A proton is a sub-atomic particle located in the nucleus of an atom. It is positively charged and weighs approximately 1 amu.

Question 3

What is a neutron?

Answer 3

A neutron is a sub-atomic particle located in the nucleus of an atom. It is neutral [no charge] and weighs approximately 1 amu.

Question 4

What is an electron?

Answer 4

An electron is a sub-atomic particle located in the sells/orbits/ energy levels around the nucleus of an atom. It is negatively charged and weighs 0 amu [1/2000].

Question 5

What is the charge on an atom on the whole and why?

Answer 5

On the whole, atoms are neutral because the number of negative electrons cancels out with the number of positive protons.

Question 6

What is the atomic number?

Answer 6

The atomic number is the number of protons (or the number of electrons) in the nucleus of an atom.

Question 7

What is the atomic mass?

Answer 7

The atomic mass is equal to the number of protons and the number of neutrons in the nucleus of an atom.

Question 8

What is an element?

Answer 8

An element is a pure substance composed of atoms that are all the same. It can be represented by a symbol.

Question 9

What is a compound?

Answer 9

A compound is a substance which is composed of two or more different kinds of atoms. It is a single substance that can be broken down into simpler substances. It can be represented by a formula.

Question 10

What is valency?

Answer 10

Valency is the joining power of an atom. It means how many bonds an atom can make. Valency depends on the outer electron energy level.

Question 11

What is the valency of the elements in each group of the periodic table?

Answer 11

Group 1: 1
Group 2: 2
Group 3: 3
Group 4: 4
Group 5: 3
Group 6: 2
Group 7: 1
Group 8(0): 0
Transition elements usually have a valency of 2 but it is variable.

Question 12

What are isotopes?

Answer 12

Atoms with the same atomic number [no. of protons] but different atomic mass [no. of protons + no. of neutrons] are called isotopes. The isotopes of an element show the same chemical properties.

Question 13

What is a chemical bond?

Answer 13

A chemical bond is the electrostatic force of attraction between the positive and negative parts of 2 or more atoms.

Question 14

What is a lattice?

Answer 14

A lattice is a regular pattern which repeats itself layer after layer. In a solid metal, the atoms are arranged in the form of a lattice.
Exception - graphite (non-metal).

Question 15

What is a metallic bond?

Answer 15

A metallic bond is the electrostatic force of attraction between the delocalised electrons and the positive nuclei of neighboring atoms.

Question 16

What are delocalised electrons?

Answer 16

The outermost electrons in an atom are strongly attracted by the nucleus but are not confined to one atom. These electrons are called delocalised electrons because they are free to roam from one atom to another.

Question 17

What are ions?

Answer 17

Atoms which are charged are called ions. Atoms that have given away outer electrons are positively charged ions and atoms that have gained outer electrons are negatively charged ions. The charge on the ion is equal to the valency.

Question 18

What is an ionic bond?

Answer 18

An ionic bond is the electrostatic force of attraction between the the positive ions from the metal atom and the negative ions from the non-metal atom.

Question 19

What are the properties of ionic compounds?

Answer 19

• High melting + boiling point.
• At room temperature, ionic compounds are solid.
• Usually soluble in water [water can break up the ionic lattice].
• Can conduct electricity: only when in an aqueous or molten state.

Question 20

What is an ionic formula?

Answer 20

The formula that includes the charge on the ions that make it up is called an ionic formula.

Question 21

What is a covalent bond?

Answer 21

A covalent bond is the electrostatic force of attraction between the positive nuclei and the shared pairs of electrons.

Question 22

What are covalent molecular structures?

Answer 22

Covalent molecular structures are the discrete molecules of elements. Inside each molecule, the atoms are held together by strong covalent bonds but between the molecules there are only weak attractions [Van der Waals forces].

Question 23

What are the properties of covalent molecular structures?

Answer 23

• Do not conduct electricity.
• Low melting + boiling points.
• Can be insoluble or soluble in water.
• Any gas or liquid at room temperature has to be a covalent molecular compound.

Question 24

What are covalent network substances?

Answer 24

Covalent network substances are giant lattices of atoms all covalently bonded to each other.

Question 25

What are the properties of covalent network substances?

Answer 25

• Do not conduct electricity.
• High melting + boiling points.
• Insoluble in water.
• Solids at room temperature.

Question 26

Why are covalent molecular substances gases at room temperature?

Answer 26

Covalent molecular substances have low melting and boiling points because when they are heated, the weak intermolecular forces between the molecules breaks [little heat energy is required]. This leads to such substances being gases at room temperature.