Chapters 4 & 5: Chemistry

Question 1

Recall that all matter is made of … and the structure of … in terms of the nucleus, protons, neutrons and electrons.

Answer 1

All matter is made of atoms.
Protons and neutrons in the nucleus and electrons orbiting on outer shells.

Question 2

Identify that the periodic table is divided into … and … and describe how the properties of some common elements are related to their position in the Periodic Table e.g. group 1, 2, 7, 8.

Answer 2

1. Periods
2. Groups
   E.g group 1 are the alkali metals.
   Group 18 are the inert or noble gases. They have valency 0 and do not react.

Question 3

Use atomic number to describe the arrangement of the periodic table.

Answer 3

No. of protons = atomic number
In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element.
Mass number= no. protons +no. Neutrons
No. neutrons= mass number-no. protons/atomic number

Question 4

Describe how electrons are arranged in shells around the nucleus.

Answer 4

There is only a certain amount of electrons on each shell, when it is full they move to the next shell.
2 on first shell, 8 on second, 8 on third

Question 5

Identify the similar electron configuration of elements in the same group and write simple electron configurations for the first three shells.

Answer 5

Group no. tells us what valency will be (how many electrons in the outer shell)
Period no. tells us how many electron shells the atom has. This increases as you go down the periods. E.g period 1 elements have 1 electron shell.
E.g The noble group (18) have the valency 0. They do not react.
Group 1 valency 1 means they lose electrons to achieve noble gas configuration. 1+ ion.
Group 17 elements need to gain one electron to achieve noble gas configuration. 1- ion

Question 6

Use the terms “reactants” and “products” to describe a
chemical equation.

Answer 6

Reactants → Products

Question 7

Write a word equation and give some examples.

Answer 7

E.g Photosynthesis: Carbon dioxide + water + → glucose + oxygen gas.
* DON’T WRITE = INSTEAD OF →*

Question 8

Define a precipitation reaction and use the solubility rules to predict reactions.

Answer 8

A precipitate reaction is a reaction in which a precipitate forms. This is a solid that forms sometimes when two clear solutions are mixed together they react and an insoluble solid or precipitate forms.
E.g potassium iodide + lead nitrate → lead iodide + potassium nitrate

Lead iodide is insoluble so is the precipitate.

Question 9

Explain how common ionic compounds form and how they are named.

Answer 9

If an atom gains or loses electrons it becomes an ion.
E.g Sodium loses one electron to form Na+1 ion.
Chlorine gains one electron to form Cl-1 ion.
The attraction between positive and negative ions results in compounds
called ionic compounds

Question 10

Explain how elements have isotopes and that some of these are unstable and decay radioisotopes.

Answer 10

Radioisotopes are radioactive isotopes of an element. If the protons and neutrons in an atom’s nucleus are strongly bonded, the atom is stable. If not then it is unstable.

Isotopes that are unstable break down into other elements by releasing different particles and energy. These isotopes are said to be radioactive.