Atomic Structure and the Periodic Table

Question 1

Where on the nuclear symbol of an atom are the atomic and mass number? What do they tell you?

Answer 1

-Mass number (on top) tells you the total number of protons and neutrons
-Atomic number (on the bottom) tells you how many protons there are

Question 2

What is relative atomic mass?

Answer 2

The average mass of all the isotopes that make up an element (taking into account the different masses and abundances).

Question 3

What is the formula for finding the relative atomic mass of an element?

Answer 3

Ar = sum of (isotope abundance x isotope mass number) / sum of all abundances of the isotope

Question 4

How do you separate out the original elements of a compound?

Answer 4

With a chemical reaction. But there is always at least one new substance made.

Question 5

How does ionic bonding work?

Answer 5

-Between a metal and non-metal
-metal atoms lose an electron to form positive ions
-non-metal atoms gain and electron to form negative ions
-the opposite charges mean that the ions are strongly attracted by electrostatic forces
-e.g. sodium chloride, magnesium oxide, calcium oxidd

Question 6

How does covalent bonding work?

Answer 6

-between non-metals
-consists of molecules
-each atom shares an electron with another atom
-E.g. carbon monoxide, water, hydrogen chloride gas

Question 7

What are the formulas for Ammonia, Sodium Carbonate and Sulfuric Acid?

Answer 7

Ammonia - NH3
Sodium Carbonate - NA2CO3
Sulfuric Acid - H2SO4

Question 8

How can mixtures be separated?

Answer 8

-filtration
-crystallisation
-simple distillation
-fractional distillation
-chromatography

Question 9

What is the difference between the properties of a mixture and the properties of a compound?

Answer 9

-The properties of a compound are completely different than the properties of the elements it’s made of
-the properties of a mixture is a mixture of the properties of the separate parts it’s made of

Question 10

How do you do paper chromatography?

Answer 10

-draw a line near the bottom of filter paper in pencil
-add a spot of ink on it and place the paper into a beaker of solvent
-place a lid on top
-as solvent soaks through, each ink moves up at a different speed
-any insoluble dies won’t move
-take the paper out and leave to dry
-end result is called a chromatogram

Question 11

When can you use filtration?

Answer 11

When you have an insoluble solid that needs to be separated from a liquid reaction mixture

Question 12

When should you use evaporation and crystallisation?

Answer 12

When you have a soluble salt to separate from a solution. But evaporation can only be used if the salt doesn’t decompose.

Question 13

How is evaporation carried out?

Answer 13

-pour solution into evaporating dish
-slowly heat solution
-it starts to get more concentrated as it evaporates
-eventually crystals form
-keep going until only crystals are left

Question 14

How is crystallisation carried out?

Answer 14

-pour solution into evaporating dish
-slowly heat solution
-once crystals start to form remove form the heat
-salt becomes insoluble in the cold and forms crystals
-filter the crystals out

Question 15

Describe the process of separating rock salt using filtration and crystallisation.

Answer 15

-grind the mixture so the salt crystals are small and easy to dissolve
-add mixture to water and stir
-filter the mixture to collect the sand
-evaporate the water so the salt forms dry crystals

Question 16

Describe the process of separating liquids using simple distillation. What is an example?

Answer 16

-solution is heated
-part with lowest boiling point evaporates first
-vapour is cooled, condensed and collected
-rest of solution is left in the flask
-e.g. separating pure water from sea water

Question 17

Why do you sometimes have to use fractional distillation instead of simple distillation?

Answer 17

because simple distillation only works if things have very different boiling points.

Question 18

Describe the process of separating liquids using fractional distillation.

Answer 18

-put mixture in a flask with fractionating column on top
-heat it
-different liquids evaporate at different temperatures
-when the temperature reaches the boiling point of the liquid with the lowest boiling point it reaches the top of the column
-other liquids may also evaporate but it gets colder towards the top of the column so they’ll condense
-the temp. can then be raised to collect the next liquid

Question 19

How did John Dalton Describe atoms at the beginning of the 19th century? Model 1

Answer 19

as different solid spheres, each one making up a different element

Question 20

What did J J Thompson conclude about the atom in 1897? What was his model called? Model 2

Answer 20

-it must contain even smaller negatively charged particles (electrons) because of his measurements of charge and mass
-the plum pudding model

Question 21

What experiment did Ernest Rutherford conduct on the atom in 1909? What did he discover and conclude? What was his model called? Model 3

Answer 21

-alpha particle scattering experiment
-fired positively charged alpha particles through thin sheet of gold
-expected particles to pass straight through
-some particles were deflected, nullifying plum pudding model
-explained this by concluding that there was a positively charged nucleus at the centre with most of the mass
-surrounded by a cloud of negative electrons which was mostly empty space
-nuclear model

Question 22

What did Niels Bohr suggest about the atom and why? Model 4

Answer 22

-if Rutherford was right the cloud would be attracted to the nucleus and the atom would collapse
-Bohr suggested that the electrons were contained in fixed shells and orbited the nucleus

Question 23

How were protons and neutrons discovered?

Answer 23

-through experimentation scientist found that the nucleus could be split into smaller particles with the same charge as a hydrogen nucleus (protons)
-around 1929 James Chadwick found evidence for neutral particles in the nucleus (neutrons)

Question 24

How was the periodic table originally organised? Why was it incorrect?

Answer 24

-in order of atomic weight
-they were incomplete and some elements were put in the wrong group

Question 25

Describe the process Dmitri Mendeleev used to devise his version of the periodic table in 1869.

Answer 25

-he took the 50 known elements and arranged them with various gaps -put them mainly in order of atomic weight but switched a few around based on properties -gaps were put in to make sure that elements with similar properties were in the same group -he predicted the properties of undiscovered elements, which were later proven

Question 26

Why are the groups of elements in the periodic table significant?

Answer 26

-group number shows how many electrons in the outer shell (except group 0) -knowing the property of an element can help you predict the properties of other elements in that group -you can make prediction about trends in reactivity

Question 27

What is the difference between a metal and a non-metal?

Answer 27

Metals can form positive ions when they react but non-metals generally don't

Question 28

Why is it easier for metals to form positive ions.

Answer 28

Unlike the non-metals, the ones on the left of the periodic table don't have many electrons to get rid of and the ones on the bottom have outer shells which are far from the nucleus meaning there's a weaker force of attraction on the electrons. This all means it's easier for the electrons to leave in a reaction.

Question 29

What basic physical properties do all metals share because of metallic bonding?

Answer 29

-strong but malleable (can be bent) -conduct heat and electricity -high melting and boiling points

Question 30

What basic physical properties do non-metals share because they don't have metallic bonding?

Answer 30

-dull looking -brittle -aren't always solids -generally don't conduct electricity -lower density

Question 31

What are the properties of transition metals?

Answer 31

-conduct heat and electricity -dense, strong, shiny -can have more than one ion -coloured -make good catalysts

Question 32

What are the properties of group 1 alkali metals?

Answer 32

-very reactive -soft -low density -increased reactivity as you go down the group -lower melting and boiling points as you go down the group -higher relative atomic mass as you go down the group

Question 33

What do the group 1 alkali metals react to form?

Answer 33

1+ ionic compounds that are generally white solids that dissolve in water to form colourless solutions

Question 34

What happens when group 1 metals react with water?

Answer 34

-react vigorously to produce hydrogen gas and metal oxides -amount of energy given out by the reaction increases as you go down the group

Question 35

What happens when group 1 metals react with chlorine?

Answer 35

-react vigorously when heated in chlorine gas -form white metal chloride salts

Question 36

What happens when group 1 metals react with oxygen? What do lithium, sodium and potassium react to form?

Answer 36

-form a metal oxide -Lithium forms lithium oxide (Li2O) -Sodium forms a mixture of sodium oxide (Na2O) and sodium peroxide (Na2O2) -Potassium reacts to form a mixture of potassium peroxide (K2O2) and potassium superoxide

Question 37

What form do each of the four main halogens take?

Answer 37

Fluorine - very reactive, poisonous yellow gas Chlorine - fairly reactive poisonous green gas Bromine - dense, poisonous, volatile red-brown liquid Iodine - dark grey crystalline solid or a purple vapour They're all molecules with pairs of atoms

Question 38

What happens to the properties of the group 7 halogens as you go down the group?

Answer 38

-less reactive (because the outer shell is further from the nucleus so its harder to gain an electron) -higher melting and boiling points -higher relative atomic masses

Question 39

What happens when halogens bond with metals?

Answer 39

-they form 1- ions called halides -the compounds form have ionic structures

Question 40

When do displacement reactions occur? Give an example

Answer 40

When a more reactive halogen reacts with the salt of a less reactive one. E.g. Chlorine can displace bromine and iodine from an aqueous solution of its salt (a bromide or iodide)

Question 41

What are the properties of the group 7 noble gases?

Answer 41

-full outer shells so they don't give up or gain electrons (not very reactive at all -monatomic gases (single non-bonded atoms) -colourless gases at room temperature -non-flammable -boiling point increases as you move down the group -relative atomic mass increases as you move down the group