C4- Chemical Patturns

Question 1

The electrons?

Answer 1

• They move around the nucleus.
• They are negatively charged.
• They are tiny. But cover a lot of space.
• The volume of their orbits determines how big the atom is.
• They have no mass.
• They are arranged in shells around the nucleus.

Question 2

The particles?

Answer 2

• Protons are heavy and positively charged.
(Relative mass is 1 and charge is +1)

• Neutrons are heavy and neutral.
(Relative mass is 1 and charge is 0)

• Electrons are tiny and negativity charged.
(Relative mass is 0.0005 and charge is -1)

Question 3

Facts about the particles?

Answer 3

• Neutral atoms have no charge overall.
• The charge in the electrons is the same size charge as the protons- but opposite.
• This means the number of protons is the same as the number of electrons in a neutral atom.
• If electrons are added or removed the atom becomes charged and is then an ion.
• The number of neutrons isn’t fixed but is usually the same amount as the protons.

Question 4

Why does each element have different number of protons?

Answer 4

It is the number of protons in an atom which decides what element it is.

Atoms of the same element all have the same number of protons. Atoms of different elements will have different number of protons.

Elements all have different properties from each other due to difference in their atomic structure.

Question 5

What are the state symbols?

Answer 5

(S)- solid

(L)- liquid

(G)- gas

(Aq)- dissolved in water

Question 6

How do elements emit different colours when heated?

Answer 6

• Lithium (Li) produces a red flame.
• Sodium (Na) produces a yellow/orange flame.
• Potassium (K) produces a lilic flame.

Question 7

How do elements give a characteristic line spectrum?

Answer 7

• When heated, the electrons in an atom vibrate and release energy as light.
• The wavelengths emitted can be recorded as a line spectrum.
• Different elements emit different wavelengths of light. This is due to each element having a different electron arrangement.
• So each element has a different pattern of wavelengths and a different line spectrum.
• This means that line spectrum can be used to identify elements.
• The practical technique used to produce a line spectrum is called “spectroscopy”.

Question 8

How did line spectrum identify new elements?

Answer 8

• Caesium and rubidium were both discovered by their line spectrum.
• Helium was discovered in the line spectrum of the Sun.

Question 9

Who was Dobereiner?

Answer 9

In the 1800s they could only measure the relative atomic mass. So the known elements were arranged in order of atomic mass.

In 1828, Dobereiner put a list of elements into groups based on their chemical properties. He put elements into groups of three- which he called triads.

The middle element of each he tried had a relative atomic mass that was the average of the other two.

Question 10

Newlands law of Octaves?

Answer 10

Newlands discovered that when you arrange elements in order of relative atomic mass, every eighth element had similar properties.

So he listed some of the elements in rows of seven.

The set of eight were called new lands octaves. However the pattern broke down on the third row- with titanium and iron messing it up.

Question 11

Why did newlands law octaves get criticised?

Answer 11

• His group contained elements that didn’t have similar properties. (E.g. Carbon)
• He mixed up metals with non metals.
• He didn’t leave any gaps for the elements that haven’t been discovered yet.

Question 12

Dmitri Mendeleev?

Answer 12

In 1869, Dmitri in Russia got 50 known elements and arranged them into table of elements. With various gaps shown.

He put the elements in order of atomic mass. But found out that he had to leave gaps in order to keep elements with similar properties in the same vertical groups.

The gaps were clever because they predicted the properties of undiscovered elements. When get were found and they fitted the pattern, Dmitri idea was confirmed.

Question 13

The periodic table?

Answer 13

• There are around 100 elements which all materials are made of.
• In the periodic table, the elements are laid out in order of increasing proton number.
• Arranging the elements like this means there are repeating patterns in the properties of the elements.
• Elements with similar properties form columns.
• The vertical columns are called groups.
• The group number tells you how many electrons are in the outer shell.
• If you know the properties of one element- you can predict the properties of other elements in that group.
• You can make predictions about reactivity.
• The rows are called periods. Each period represents another full shell of electrons.

Question 14

Information from the periodic table?

Answer 14

By looking at the table you can find out:

• The name and symbol of each element.
• The proton number of each element. This tells you the number of protons in the nucleus.
• The relative atomic mass of each element. This tells you the total number of protons and neutrons in the nucleus.
• You can calculate the number of neutrons by subtracting the the number of protons from the atomic mass.

Question 15

Electron shell rules?

Answer 15

• Electrons always occupy shells (sometimes called energy levels)
• The lowest energy levels are always filled first.
• Only a certain number of electrons are allowed in each shell.
• First shell- 2 electrons
• Second shell- 8 electrons
• Third shell- 8 electrons
• Atoms are more satisfied with full electron shells.
• In most atoms the outer shell is not full- making the atom want to react.
• An elements electron arrangement determines its chemical properties.

Question 16

What are ions?

Answer 16

• When an atom gains or loses an electron they form charged particles called ions.
• Ions can be made from single atoms or groups of atoms.
• When an atom gains or loses electrons- all they are trying to do is get a full outer shell.

Question 17

Atoms in Group 1?

Answer 17

• All the atoms in group 1 have one electron in their outer shell.
• They want to get rid of the one electron on the outer shell- then they will have full outer shells- how they like it.
• When group 1 elements lose an electron, they form positive ions.

Question 18

Atoms in group 7?

Answer 18

• All elements in group 7 have outer shells which are nearly full.
• They want to gain one more electron to have a full outer shell.
• When group 7 elements gain one extra electron they form negative ions.

Question 19

Ionic bonding?

Answer 19

• Oppsitely charged ions are strongly attracted to each other.
• They leap at the first passing ion with an opposite charge and stick to it- forming an ionic bond.
• Compounds formed between group 1 and group 7 elements are held together by ionic bonds. They are ionic compounds.

Question 20

Ionic compounds?

Answer 20

• Solid ionic compounds like sodium chloride are made up of a giant lattice of ions. Each lattice forms a single crystal.
• When ionic compounds become molten or are dissolved in water they can conduct electricity because the ions are able to move.
• The fact that molten compounds of metal and non metal can conduct electricity is used as evidence that they’re made up of ions.

Question 21

Group 1- Alkali metals?

Answer 21

• Group 1 includes lithium, sodium and potassium.
• They all have one outer shell and are very reactive.
• When alkali metals react they all form similar compounds.
• The alkali metals are shiny when freshly cut. But quickly react with the oxygen in moist air and tarnish.
• As you go down group 1 the alkali metals become more reactive- because the outer electron is easily lost because it’s further from the nucleus.
• The alkali metals have a higher density because the atoms have more mass.
• They have a lower melting and boiling point.

Question 22

Reaction with cold water produces hydrogen?

Answer 22

• When lithium, sodium or potassium are put in water - they react vigorously.
• They move around the surface- fizzing furiously.
• They produce hydrogen. Potassium gets hot enough to ignite it. If it hasn’t already been ignited by the reaction, a lighted splint will indicate hydrogen by producing the “squeaky pop” as it ignites.
• The reaction makes an alkaline solution. - this is why group 1 metals are alkali metals.
• A hydroxide of the metal forms e.g. Sodium hydroxide (NaOH), potassium hydroxide (KOH), or lithium hydroxide (LiOH).
• This experiment shows the relative re activities of the alkali metals. The more violent the reaction, the more reactive the alkali metal is.

Question 23

Reaction with chlorine produces salts?

Answer 23

• Alkali metals react vigorously with chlorine.
• This reaction produces colourless crystalline salts. E.g. Lithium chloride (LiCl), sodium chloride (NaCl) and potassium chloride (KCl)

Question 24

The halogens?

Answer 24

• Group 7 elements include chlorine, bromine and iodine.
• They have 7 outer electrons. This makes them very reactive.
• As you go down group 7 they become less reactive. Because the outer electrons are further from the nucleus and so additional electrons are attracted less strongly.
• They have a higher melting and boiling point.

Question 25

Halogens with colours vapours?

Answer 25

• Fluorine - very reactive- poisonous yellow gas at room temperature and pressure.
• Chlorine - fairly reactive- poisonous dense green gas at room temperature and pressure.
• Bromine- dense poisonous orange volatile liquid at room temperature and pressure forms an orange gas.
• Iodine- dark grey crystalline solid at room temperature or a purple vapour.

Question 26

What is a displacement reaction?

Answer 26

Is where a more reactive element displaces a less reactive element from a compound.

Question 27

Halogens reacting with iron?

Answer 27

They react with iron to form coloured solids called iron halides.

The reactions become less vigorous as you go down the group.

Question 28

Halogens reacting with alkali metals?

Answer 28

The halogens react with alkali metals to form salts called metal halides.

The reactions become less vigorous as you go down the group.

Question 29

Hazard symbols?

Answer 29

Oxidising- Provides oxygen which allows other materials to burn more fiercely.

Highly flammable- Catches fire easily.

Toxic- Can cause death either by swallowing, breathing in or absorption through skin.

Explosive- Can explode.

Corrosive- Attacks and destroys living tissues. Including eyes or skin.

Question 30

Alkali metals Safety?

Answer 30

• They are really reactive and can combust suddenly.
• If they come into contact with water vapour in the air- there would be a violent reaction depending on how much alkali metal there is. So they are stored under oil to prevent this.
• If Alkali metals are touched with bare hands- the sweat on your skin is enough to cause a reaction with heat and a corrosive hydroxide.
• Every apparatus should be kept dry.
• The alkaline solutions formed are corrosive and may cause blistering.

Question 31

Halogens safety?

Answer 31

• Group 7 elements are harmful- chlorine and iodine are toxic.
• Fluorine is the most reactive halogen. It’s too dangerous in the lab.
• Liquid bromine is corrosive. So contact with skin is avoided.
• Halogens have poisonous vapours that irritate the respiratory system and the eyes. They must be in a fume cupboard so they can’t be breathed in.

Question 32

The nucleus?

Answer 32

• In the middle of the atom.
• It contains protons & neutrons.
• It has positive charge. Due to the protons.
• The whole mass of the atom is concentrated in the nucleus.
• However it is tiny compared to the whole atom.