chemistry

Question 1

what does atoms contain?
what is the radius of an atom?

Answer 1

They contain:
-Protons
-Neutrons
-Electrons

Radius of an atom- 1x10-10 m/0.1 nanometers

Question 2

where is nucleus located in the atom?
what does nucleus contain?
what is the radius of nucleus?
what is the charge of the nucleus and why?
where is the whole of the mass located?

Answer 2

• Its located in the middle
• protons and neutrons
• radius- 1X10-14m
• it has positive charge because of the protons
• concentrated in the nucleus

Question 3

what does electrons do in the atom?
what are 5 facts about the electron?

Answer 3

• move around the nucleus in electron shells
  5 facts:
  -volume of their orbits determines the size of the atom
• they have no mass
• negatively charged and tiny /take a lot of space

Question 4

why do atoms have no charge overall?
why do the charges cancel out?

Answer 4

• This is because they have the same number of protons as electrons
• They cancel out because electrons same size as the charge of a proton

Question 5

what is an ion?
why does an ion have an overall charge?

Answer 5

• ion is an atom or a group of atoms that has lost or gained electrons
• number of protons doesn’t equal to the number of electrons
  example- an ion with 2- charge has two more electrons than protons

Question 6

what does the atomic number tell you?
what does the mass number tell you?
how do you work out neutrons?

Answer 6

• atomic number- how many protons/electrons
  -mass number- total number of protons and neutrons
  -To work out neutrons you subtract mass number and atomic number

Question 7

what is an element?
what sub atomic particle decides the type of atom eg?

Answer 7

-Element is a substance made up of atoms that all have the same number of protons in their nucleus
-Protons decide
example: atom has one proton in the nucleus its called hydrogen an atom that has 2 protons is called helium

Question 8

what does a substance which only contains atoms with the same number of protons called?

Answer 8

Element

Question 9

how can atoms be represented and an example?

Answer 9

-Atoms can be represented by 1 or 2 letter symbol
example- c=carbon
mg=magnesium

Question 10

what are isotopes?
what do isotopes have the same of and different of?

Answer 10

-Different forms of the same element which have the same number of protons but different number of neutrons
-Same atomic number but different mass numbers

Question 11

why is relative atomic mass number used instead of mass number?

Answer 11

-many elements can exist as a number of different isotopes but relative atomic mass instead of mass number when referring to the element as a whole.

Question 12

how do you work out relative atomic mass?

Answer 12

sum of (Isotope abundance × isotope mass number)
DIVIDED BY
sum of abundance of all the isotopes

Question 13

what happens when elements react?
what are compounds?

Answer 13

-when elements react atoms combine with other atoms to form compounds
-compounds are substances formed from two or more elements the atoms of each are in fixed proportions throughout the compounds and they’re held together by a chemical bond

Question 14

what does making bonds do?
what is needed to separate original elements from a compound?

Answer 14

-Making bonds 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
-A chemical reaction is needed because its difficult

Question 15

what does compounds formed from non-metals and metals consist of?
which metals form positive ions and negative ions?
what is ionic bonding and examples

Answer 15

-Consist of ions
-Metal atoms lose electrons to form positive ions
-Non metals gain electrons to form negative ions
-Opposite charges of ions mean that there strongly attracted to each other eg magnesium oxide, calcium oxide and sodium chloride

Question 16

what do compounds formed from non metals consists of?
what is covalent bonding and examples?

Answer 16

-They consists of molecules
-Covalent bonding is each atom shares an electron with another atom eg hydrogen chloride gas, carbon monoxide and water

Question 17

why is the properties of a compound totally different from the properties of the original elements?

Answer 17

TO explain:
Iron a lustrous magnetic metal and sulfur a yellow powder react compound forms iron sulfide is a dull grey solid dump and doesnt behave anything like iron or sulfur

Question 18

what are examples of compounds represented by an symbol? explain them?
what does the brackets in a formula do?

Answer 18

EXAMPLE:
co^2 is a compound formed from a chemical reaction between carbon and oxygen.It contains 1 carbon atom and 2 oxygen atoms

Brackets eg calcium hydroxide in Ca(OH)2.The little number outside of the bracket applies to everything inside the bracket.So theres 1 calcium atom 2 oxygen 2 hydrogens

Question 19

what are some compound formulas?

Answer 19

-Ammonia=NH3
-Carbon monoxide=CO
-Calcium chloride=Cacl2
-Sulfuric acid=H2so4

Question 20

what is an example of a chemical equation?

Answer 20

Methan+oxygen—carbon dioxide + water

Left hand methane and oxygen are reactants because they react with each other
Right hand carbon dioxide and water they are called products they have been produced from reactants

Question 21

what is the difference between a compound and a mixture?
what are the parts of a mixture?

Answer 21

-The difference is a compound doesnt have a chemical bond between the different parts of a mixture
-Parts of a mixture can either be elements or compounds and they can be separated out by physical methods

Question 22

what is air a mixtures of?
what is crude oil a mixture of?

Answer 22

-Air mixtures of gases mainly nitrogen oxygen carbon dioxide and argon. The gases can be separated fairly easy
-Crude oil is a mixture of different length hydrocarbon molecules

Question 23

what are the 10 steps of chromatography?

Answer 23

1) Draw a line near the bottom of a sheet of filter paper (use a pencil they are insoluble)

2)Add a spot of ink to the line and place sheet into the beaker of the solvent

3)The solvent used depends on what’s being tested. Some compounds dissolve well in water but sometimes other solvents like ethanol are needed

4)Make sure the ink isn’t touching the solvent

5)Place a lid on top of the container to the stop the solvent from evaporating

6) The solvent seeps up the paper carrying the ink with it

7)Each different dye in the ink will move up the paper at different rates so the dyes will separate out. Each dye will form a spot in a different place

8) If any of the dyes in the ink are insoluble in the solvent you used they will stay on the baseline

9) when the solvent has nearly reached the top of the paper take the paper out of the beaker and leave it to dry

10) The end results is a pattern of spots called a chromatogram

Question 24

what are electrons occupied by?
which energy level is always filled first?
how many electrons are let in the 1,2,3 shells?

Answer 24

-Electrons are occupied by shells
-Lowest energy level is always filled first
-1st shell-2
-2nd shell-8
-3rd shell-8

Question 25

when atoms much happier?
what happens if the outer shell is not full?

Answer 25

-When atoms are much happier they have full electron shells like noble gasses
-In most atoms the outer shell is not full and this makes the atoms want to react to fill it

Question 26

EXAMPLE TO WORK OUT ELECTRONIC STRUCTURES

Answer 26

1)Nitrogen atomic number is 7 this means it has 7 protons so it must have 7 electrons
2)Follow the electron shell rules.1 shell on can take 2 electrons and 2 shell can take a max of 8