C1 Compounds (page 98)

Question 1

What are compounds?

Answer 1

compounds are substances formed from two or more elements, the atoms of each are in fixed proportions throughout the compound and they’re held together by chemical bonds.

Question 2

Examples of compounds which are bonded ionically include?

Answer 2

sodium chloride
magnesium oxide
calcium oxide

Question 3

How do compounds form?

Answer 3

When elements react, atoms combine with other atoms to form compounds

Question 4

What is involved when making bonds?

Answer 4

this involves atoms giving away, taking or sharing electrons.

Only the electrons are involved - the Nuclei of the atoms aren’t affected at all when a bond is made

Question 5

how can you separate the original element of a compound after it is bonded together with another electron?

Answer 5

its usually difficult to separate the original element of a compound out again - a chemical reaction is needed to do this.

Question 6

A compound which is formed from a metal and a non-metal consists of what?

Answer 6

Ions

The metal atoms lose electrons to form positive ions, and the non-metal atoms gain electrons to form negative ions.

Question 7

What do Ionic bonding mean?

Answer 7

The opposite charges (positive and negative) of the ions mean that they’re strongly attracted to each other., this is called ionic bonding

Question 8

What is a compound formed from non-metals consist of?

Answer 8

molecules.

Question 9

What is convalent bonding?

Answer 9

Each atom shares an electron with another atom between non metal atoms only. this is called convalent bonding

Question 10

What examples are there of compounds that are bonded convalently?

Answer 10

Hydrogen Chloride gas

carbon monoxide,

water

Question 11

are properties of a compound usually the same or totally different from the properties of the original elements?

Answer 11

They are usually totally different.

eg; if iron (a lustrous magnetic metal) and sulfur (a nice yellow powder) react, the compound formed (iron sulfide) is a dull grey solid lump, and doesnt behave anythig like either ion or sulfur

Fe + S &raquo_space;»»»» FeS (compound)

Question 12

Elements are represented by symbols, how is compounds represented?

Answer 12

by formulas

The formulas are made up of elemental symbols in the same proportions that the elements can be found in the compound

example:

Carbon dioxide, CO2, is a compound formed from a chemical reaction between carbon and oxygen. It contains 1 carbon atom and 2 oxygen atoms.

or

the formula of sulfuric acid is H2SO4, so each molecule contains 2 hydrogen atoms, 1 sulfur atom and 4 oxygen atoms.

There might be BRACKETS in a formula, eg;
calcium ydroxide is Ca(OH)2. The little number outside the bracket applies to EVERYTHING inside the BRACKETS. so in Ca(OH)2 there’s 1 calcium atom, 2 oxygen atoms and 2 hydrogen atoms

Question 13

How many atoms are in one particle of Na2CO3?

Answer 13

(2 x Na) + (1 x C) = (3 x O) = 6 (1 mark)

Question 14

A compound has the formula Al2(SO4)3. Name the elements and state how many atoms of each element are represented in its formula? (1 mark)

Answer 14

Aluminium - 2 atoms, sulfur - 3 atoms and oxygen - 12 atoms (1 mark)