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Chemistry > Topic 1 > Flashcards

Topic 1 Flashcards

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1
Q

Atoms

A
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2
Q

What is an atoms radius?

A

0.1 Nanometers

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3
Q

The nucleus

A
  • in the middle of the atom
  • it contains protons and neutrons
  • it is positive charge
  • almost the whole mass of the atom is concentrated in the nucleus
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4
Q

The electrons

A
  • move around nucleus in electron shells
  • negatively charged
  • volume of their orbits determines the size of their atoms
  • virtually no mass
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5
Q

Why are atoms neutral?

A

Because there is the same number of electrons to protons meaning the positive and negative balance cancel each other out.

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6
Q

Atomic number and mass number

A
  • the atomic number tells use how many protons their are (on the bottom)
  • the mass number tells you the total number of neutrons and protons in the atom
  • to get the number of neutrons just subtract the atomic number from mass number
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7
Q

Elements

A
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8
Q

What is an element?

A

An element is a substance made up of atoms that all have the same number of protons in their nucleus?

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9
Q

How many elements are there?

A

About 100 different elements

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10
Q

What are isotopes?

A

Isotopes are different forms of the same element, which have the same number of protons but different number of neutrons.

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11
Q

Formula for relative atomic mass (Ar)

A

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

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12
Q

Compounds

A
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13
Q

What is a compound?

A

Substances formed from two or more elements.

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14
Q

Making bonds

A

-this involves atoms giving away, taking or sharing electrons

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15
Q

Compounds formed through non-metal and metal

A
  • ionic bonding
  • non-metal gains electrons to form negative ions
  • metal looses electrons so becomes positive
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16
Q

Compounds formed through non-metals

A
  • consists of molecules
  • each share an electron with the other atom
  • covalent bonding
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17
Q

Mixtures and Chromatography

A
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18
Q

Mixtures

A

-no chemical bonds

19
Q

Paper Chromatography (practical)

A

1) draw a line on the bottom of the filter paper using a pencil (pencil marks are insoluble so want dissolve the solvent)
2) add a spot of ink to the line and place the filter paper in the beak of the solvent (e.g. water)
3) make sure ink does not touch the solvent
5) place a lid on the container to stop the solvent evaporating
6) solvent speeds up the paper carrying the ink with it
7) each different dye will move up the paper at a different rate so the dyes will separate out, each dye will form a spot on a different place
8) if any dyes are insoluble than they will stay on the baseline and will not dissolve
9) when solvent reached near the top, take paper out and leave to dry
10) the end result is called chromatogram

20
Q

Filtration

A

Filtration separates soluble solids from liquids

21
Q

Evaporation

A

1) pour solution into an evaporating dish
2) slowly heat solution,, solvent will evaporate and solution will get more concentrated and crystals will form
3) keep heating evaporating dish until dry crystals are left
Separating soluble solids from solutions

22
Q

Crystallisation

A

1) pour solution into evaporating dish and gently heat solution, some of solvent will evaporate and solution will get more concentrated
2) once some solvent has evaporated, or when you see crystals start of form, remove dish from the heat and leave solution to cool
3) salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
4) filter crystals out of solution, and leave them in a warm place to dry. You can use a drying oven or a desiccator
Separating soluble solids from solutions

23
Q

Filtration and Crystallisation to separate rock salt

A
  • salt dissolves in water but sand doesn’t
    1) grind mixture to make sure salt crystals are small so will dissolve easily
    2) put mixture in water and stir
    3) filter mixture, grains of sand won’t fit through tiny holes in filter paper, so they collect on the paper instead, salt passes through the filter paper as it is part of the solution
    4) evaporate water from salt so that it forms dry crystals
24
Q

Distillation

A
25
Q

Simple Distillation

A
  • used to separate out solutions
    1) simple distillation is used for separating out a liquid from a solution
    2) solution is heated, part of solution with lowest boiling point evaporates first
    3) vapour is than cooled, condenses and collected
    4) rest of solution is left behind in the flask
    5) you can use simple distillation to get pure water from seawater. Water evaporates and is condensed and collected, eventually you will end up with just salt left in flask
26
Q

Fractional Distillation

A

To separate a mixture of liquids

1) put your mixture in a flask and stick a fractionating column on top, than heat it
2) diff liquids have diff boiling points so will evaporate at diff temperatures
3) liquid with lowest boiling point will evaporate first, when thermometer matches boiling point it will reach the top of the column
4) higher boiling points will evaporate but will only get half the way up of the column before condensing and running back down the column
5) when first liquid has been collected you raise the temperature until the next one reaches the top

27
Q

The History of the Atom

A
28
Q

Theories of the atomic structure

A

1) 19th century John Dalton described atoms as solid spheres, and said that different spheres made up different elements
2) 1887 J J Thomson concluded from his experiments that atoms weren’t solid spheres and the atom contained electrons, and this was called the ‘plum pudding model’
3) the plum pudding model shows the atom as a ball of positive charge with electrons stuck in it

29
Q

Rutherford

A

In 1909 Ernest Rutherford and Ernest Marsden conducted the alpha particle scattering experiments, they fired charged alpha particles at an extremely thin sheet of gold. Most passed through but some were deflected back. This was made to be the nuclear model, this has a tiny positive charged nucleus at the center where most of the mass was concentrated at, and the rest of the atom was empty space.

30
Q

Niels Bohr

A

He suggested all the electrons contained in shell and orbit the nucleus in fixed shells

31
Q

James Chadwick

A

Discovered neutrons

32
Q

Electronic structure

A
33
Q

Electron shell rules

A
  • lowest energy levels are the ones closest to the nucleus and always filled first
  • only a certain number of electrons are allowed in each shell: 1st shell is 2, 2nd shell is 8 and 3rd shell is 8
  • atoms wants a full outer shell
  • in most atoms the outer shell is not full and this makes the atom want to react to fill it
34
Q

Development of the periodic table

A
35
Q

How were elements arranged in the early 1800s?

A

They were arranged by atomic mass, and categorised in the physical and chemical properties and their relative atomic mass.

36
Q

Dmitri Mendeleev

A

-he put the elements in order of atomic mass
-he switched order if properties meant needed to be changed
Example: he switched Te and I, Iodine has a smaller mass but placed after tellurium as it had similar properties to the elements in that group.
Example: he left gaps in the table for elements that were not discovered yet, these were ekasilicon and germanium

37
Q

The modern periodic table

A
  • 100 ish elements
  • elements are ordered in increasing atomic number
  • metals are found on the left
  • non-metals are found on the right
  • elements with similar properties form columns and these vertical columns are called groups
  • group number tells you how many electrons are in the outer shell apart from helium in group 0
  • if you know properties of one element you can predict properties of elements in that group and predict trends as you go down the group
  • rows are called periods and each new period represents another full shell of electrons
38
Q

Metals and non-metals

A
39
Q

Metals

A
  • most elements are metals
  • they are towards the bottom and to the left of the periodic table
  • involve metallic bonding
  • strong
  • malleable
  • good conductor of electricity and heat
  • high boiling and melting points
40
Q

Non-metals

A
  • far from the right and top of the periodic table
  • harder for them to form positive ions as they have more electrons
  • low density
  • brittle
  • don’t conduct electricity or heat
41
Q

Group 1 elements

A
  • alkali metals
  • one electron on outer shell
  • soft and low density
  • increases activity as the outer electron is easily lost as the attraction between the nucleus and electron decreases, because the electron is further away from the nucleus, the further down the group you go, low melting and boiling points, higher relative atomic mass
  • form ionic compounds with non-metals
  • they form 1+ ions
  • reaction with water produced hydrogen gas: when put in water they react vigorously
  • reaction with chloride produced salt
  • reaction with oxygen produced a metal oxide
42
Q

Group 7 elements

A
  • halogens: Fluorine is yellow, chlorine is green, bromine is red-brown, iodine is dark grey
  • as you go down the group halogens: become less reactive as it is harder to gain an extra electron because the outer shell’s further from the nucleus, they have higher boiling and melting points, have a higher relative atomic mass
  • they form molecular compounds as they react with non-metals via covalent bonding
  • they form ionic bonds with metals: halogens form 1- ions (halides), the compounds that form have ionic structures
  • more reactive halogens will displace less reactive ones
43
Q

Group 0

A
  • noble gases
  • eight electrons on outer shell (full outer shell)
  • monatomic gases (single atoms not bonded to each other)
  • colourless gases at room temperature
  • internet- non-flammable
  • as you go down the group boiling points of noble gases increase as well as number of electrons which leads to a greater intermolecular forces between them which they need to overcome

Chemistry (10 decks)

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