8 The Periodic Table

Question 1

Periodic table

Answer 1

A table that lists all the elements in ascending order of atomic number. Also organised by groups and periods, which detail the electronic configuration of the elements.

Question 2

Metal

Answer 2

An element with atoms that are metallic bonded and tends to lose electrons during reactions.

Question 3

Non-metals

Answer 3

An element that is not a metal. Tends to accept electrons during reactions.

Question 4

Group

Answer 4

A term used in chemistry to describe a column in the Periodic Table. The elements within a group have similar chemical properties as they all have the same number of electrons in the outer shell.

Question 5

Period

Answer 5

A term used in chemistry to describe a horizontal row in the Periodic Table. The period number tells you how many electron shells an element has.

Question 6

Noble gas

Answer 6

Elements from Group VIII of the Periodic Table. They are unreactive as their outer shells are full of electrons.

Question 7

Nucleon number

Answer 7

The combined number of protons and neutrons in the nucleus of an atom. The nucleon number also represents the mass of an atom and is also known as the mass number.

Question 8

Proton number

Answer 8

The number of protons found in the nucleus of an atom. The number of protons in its nucleus defines an atom. Also called the atomic number.

Question 9

Properties of metals

Answer 9

Metals
Large atomic radius
Conduct heat and electricity
Have a range of melting point values
Malleable and ductile
Shiny

Question 10

Properties of non-metals

Answer 10

Non-metals
Smaller atomic radius
Do not conduct heat or electricity*
Generally low melting point values
brittle
Dull

Question 11

Metaloids

Answer 11

Elements that display properties of both metals and non-metals.

Question 12

Relationship between Group number and Period number with electron configuration

Answer 12

The period number is the same as the number of electron shells that an element has.
The group number of an element is the same as the number of electrons it has in its outer shell.

Question 13

Ions form when atoms lose or gain electrons.

Answer 13

Metal atoms lose electrons to form positively charged ions.
Non-metal atoms gain electrons to form negatively charged ions.

Question 14

Covalent radius

Answer 14

A measure of the radius of an atom. Each element has a different nucleus and electron configuration so the size of the atom differs. Plural is covalent radii.

Question 15

Why covalent radius increases as you go down a group?
Why covalent radius decreases as you go across a period?

Answer 15

You would expect the covalent radius to increase as you go down a group as the number of shells of electrons increases. Each time a new outer shell is added, the radius increases.
As you go across a period, electrons fill up the same electron shell and the number of protons in the nucleus increases. This increases the strong attractive force and pulls the electron shells closer to the nucleus.

Question 16

Alkali metals

Answer 16

Metal elements from group I of the Periodic Table. Readily form alkaline hydroxides on reaction with water.

Question 17

Properties of alkali metals

Answer 17

As the elements in Group I share the same number of electrons in their outer shell

The time taken for a freshly cut element to tarnish decreases going down the group, showing that the reactivity increases going down the group.

They all have low densities. Some will even float on water.

The melting points are relatively low.

They metals react vigorously with water to produce a metal hydroxide and hydrogen gas.

Question 18

Relationship between density and Alkali metals

Answer 18

Lithium, sodium and potassium are less dense than water, so they float on water when reacting with it. The pattern is for the density of the Group I elements to increase going down

Question 19

Relationship between Melting point and Alkali Metals

Answer 19

The melting point for lithium is quite low for a metal. The pattern going down the group is for the melting point to decrease

Question 20

Alkali metals reaction with metals

Answer 20

All Group I metals react vigorously with water to produce a metal hydroxide and hydrogen gas.

Question 21

Lithium reaction with water

Answer 21

The reaction can be seen on the surface of the water. This is because lithium is less dense than water. As hydrogen gas is given off by the reaction, effervescence can be seen. The piece of lithium will often move around on the surface of the water due to the hydrogen gas being given off. The water will become slightly alkaline because of this reaction.

Question 22

Sodium reaction with water

Answer 22

The reaction of sodium with water is very similar to the reaction of lithium, however, the reaction is much more vigorous and more heat is given off. The piece of metal will move around the surface of the water faster and the reaction will usually finish quite quickly.

Question 23

Potassium reaction with water

Answer 23

When potassium reacts with water, it produces enough heat to ignite the hydrogen gas produced. The flame produced is a lilac colour. As the reaction is so vigorous, the potassium may begin to hop around on the surface of the water.

Question 24

Halogens

Answer 24

Elements belonging to Group VII in the Periodic Table.

Question 25

Trends in the halogens in colour

Answer 25

The trend down the group for colour is increasing darkness.

Chlorine is a green gas.
Bromine is a dark red liquid.
Iodine is a dark purple solid.

Question 26

Density in halogens

Answer 26

The trend down the group is for increasing density.
Fluorine and chlorine are only found as a gas at room temperature.
Bromine exists as a liquid and a vapour, where iodine is found as a solid.

Question 27

Melting points in halogens

Answer 27

As you go down the group, the melting points increase.

Question 28

Reactivity of the halogens

Answer 28

The reactivity of halogens decreases going down the group. This is because, with seven electrons in the outer electron shell, halogens react by attracting an electron to gain a full outer shell. As we move down the group, the ability of the elements to attract an extra electron to complete the outer shell weakens. This means that chlorine is much more reactive than iodine and fluorine is the most reactive halogen.

Question 29

Displacement reaction

Answer 29

A reaction where a less reactive element is removed from a compound by a more reactive element.

Question 30

Halide salts

Answer 30

Salts formed from halogens such as fluorine, chloride, bromide and iodide.

Question 31

An example of a displacement reactions of halogens with other halide ions

Answer 31

An example of this would be with potassium iodide. If we add chlorine gas, as chlorine is more reactive, the iodine will be displaced from the compound to form potassium chloride.

potassium iodide + chlorine → potassium chloride + iodine
2KI(aq) + Cl2(g) → 2KCl(aq) + I2(aq)

This is an example of a redox reaction

Question 32

Reactivity series

Answer 32

A list in which elements are ordered according to their reactivity. The most reactive elements are listed at the top.

Question 33

Noble gases

Answer 33

Elements from Group VIII of the Periodic Table. They are (unreactive) as their outer shells are full of electrons. They are colourless gases that exist as single atoms, which is why they are sometimes referred to as (monatomic).

Question 34

The appearance of the halogens at RTP

Answer 34

Chlorine, a pale yellow-green gas
Bromine, a red-brown liquid
Iodine, a grey-black solid

Question 35

Transition metals

Answer 35

Metal elements from the central block of the Periodic Table.
They are elements that have ions with variable oxidation numbers, including iron(ll) and iron(lll)

Question 36

Properties of transition metals

Answer 36

Physical
have high densities
have high melting points
High strength
Chemical
form coloured compounds
often act as catalysts as elements and in a compound
Have ions with variable oxidation numbers

Question 37

Calcium reaction with water

Answer 37

For calcium the solid metal would sink, and bubbles would be produced on the surface of the metal but they would be produced much less slowly. As the metal disappears the solution will become cloudy as calcium hydroxide is insoluble.

Question 38

Magnesium reaction with steam

Answer 38

Magnesium burns in steam to produce white magnesium oxide and hydrogen gas.

Question 39

Magnesium, iron and zinc reaction with dilute acid

Answer 39

With magnesium, bubbles would form on the surface and the metal would slowly disappear. With zinc, bubbles would form but very slowly. Iron would react so slowly it may be difficult to observe.