S1 SCI CHAP 8 MODEL OF MATTER

Question 1

Describe the structure of an Atom.

Answer 1

• Each atom is made up of even smaller particles known as sub-atomic particles. Each atom consists of 3 types of sub-atomic particles- protons, neutrons, and electrons.

Question 2

Where are the protons and neutrons located?

Answer 2

The protons and neutrons are located in the nucleus of the atom.

Question 3

Where are the electrons located?

Answer 3

The electrons are located in the orbitals of the atom.

Question 4

What does the mass number represent?

Answer 4

The mass number represents the sum of the number of protons and the number of neutrons in an atom.

Question 5

What is the mass, and charge of a proton?

Answer 5

1, 1+

Question 6

What is the mass, and charge of a neutron?

Answer 6

1, 0

Question 7

What is the mass, and charge of an electron?

Answer 7

1/1840, 1-

Question 8

Why is an atom electrically neutral?

Answer 8

An atom contains an equal number of protons and electrons. A proton has a positive charge, whereas an electron has a negative charge. Hence, the positive charge and negative charge cancel each other out, and a neutron is neutral, making an atom electrically neutral.

Question 9

What is the term electronic configuration/electronic structure of an atom?

Answer 9

The electronic configuration/electronic structure is the arrangement of electrons in an atom.

Question 10

What are the terms valence shell/outer shell and valence electrons of an atom?

Answer 10

The valence/outer shell of an atom refers to the shell that is furthest away from the nucleus of the atom. Valence electrons are the electrons found in the valence shell.

Question 11

What are isotopes?

Answer 11

Isotopes are atoms of the same lement which have the same number of protons, electrons, but different number of neutrons.

Question 12

How is a molecule formed?

Answer 12

A molecule is made up of 2 or more atoms chemically combined by covalent bond.

Question 13

What are noble gases?

Answer 13

Noble gases are elements that belong to group 15 of the P.T. The atoms of N.G. are stable and unreactive. They exist as single atoms. Noble gases also have a full or complete valence shell.

Question 14

How are ions formed?

Answer 14

ions are formed when atoms lose or gain electrons resulting in a charged particle as the number of protons and electrons are not equal.

Question 15

How are cations formed?

Answer 15

When a metallic atom loses electrons to form a positively-charged atom called cations.

Question 16

How are anions formed?

Answer 16

When a non-metallic atom gains electrons to form a negatively-charged atom called an anion.

Question 17

what are ionic bonds and how are they formed?

Answer 17

Ionic bonds are formed between two or more atoms by the transfer of one or more electrons between atoms. They are the electrostatic bond between two oppositely charged ions.

Question 18

Name the general rules for naming an ionic compound.

Answer 18

1. A compound made from 2 elements has a name that ends in -ide.
2. Compounds that contain the hydroxide ion (OH-) are named a hydroxide. e.g. potassium hydroxide.
3. Compounds containing negatively charged polyatomic ions usually have names ending with ‘-ate’. e.g. copper (II) sulfate.

Question 19

Name the general rules for writing chemical formulae of an ionic compound.

Answer 19

1. The symbol of the metallic element is written first.
2. The number of atoms is written as a subscript to the right of the atom’s symbol.
3. The subscripts are the simplest set of whole numbers.
4. Do not write the subscript ‘1’.
5. If there is more than one polyatomic atom, the formula of that ion is placed within brackets.
6. The formula of an ionic compound is constructed by balancing the charges on the positive and negative ions.
7. All the positive charges must equal all the negative charges in an ionic compound.

Question 20

What are chemical formulae?

Answer 20

another way to represent molecules.

Question 21

Name some common cations and their charges.

Answer 21

sodium ion (+)
calcium ion (2+)

Question 22

Name some common anions and their charges.

Answer 22

chloride iron (-)
oxide ion (2-)

Question 23

The following LO may be used in context in assessments

• Show an appreciation of how in practice, models are constructed, justified and continuously revised as they are used to probe new phenomena and collect additional data (e.g. the various atomic models)

Question 24

The following LO may be used in context in assessments

• Show an awareness that technologies resulting from knowledge of the atom have created social and ethical issues, risks and costs (e.g. atomic bomb)

Question 25

Which of the following is made up of only one atom?

A: A drop of water
B: A crystal of common salt
C: A sheet of aluminium foil
D: A grain of sand

Answer 25

C