Atomic Structure And The Periodic Table Flashcards
1
Q
Radius of an atom
A
0.1 nanometers
2
Q
Nucleus of an atom
A
- middle of the atom
- contains protons and neutrons
- radius of around 1x10^-14m (1/10,000 of the radius)
- positive charge from the protons
- almost the whole mass is concentrated in the nucleus
3
Q
Electrons
A
- move around nucleus in electron/energy shells
- negatively charged and tiny; cover a lot of space
- volume of orbits determines size of the atom
- virtually no mass
4
Q
Why do atoms have a neutral charge?
A
- same number of protons and electrons
- charges cancel out
- if number of protons and electrons are not equal, it is known as an ion
5
Q
Atomic Number
A
Number of protons in one atom of an element
6
Q
Mass Number
A
Total number of protons and neutrons in the atom
7
Q
Element
A
- substance that contains atoms all with the same number of protons
- e.g. all hydrogen atoms have 1 proton
8
Q
Isotope
A
- different form of the same element, which has the same number of protons but a different number of neutrons
- same atomic number but different mass numbers
- e.g. C-12 has 6 protons and 6 neutrons but C-13 has 6 protons and 7 neutrons
9
Q
Relative Atomic Mass
A
Average mass, taking into account the different masses and abundances (amounts) of all the isotopes that make up the element
10
Q
Relative Atomic Mass Formula
A
Ar = sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes
11
Q
Compounds
A
- substances formed from two or more elements
- atoms of each element are in fixed proportions
- held together by chemical bonds
12
Q
Reactants & Products
A
- reactants are on the left side of the equation
- elements/compounds at the beginning of the reaction
- products are on the right side of the equation
- elements/compounds at the end of the reaction
13
Q
Why must symbol equations be balanced?
A
- must be the same number of atoms on each side of the equation
- numbers put in front of formulas, as formula of compound cannot be changed
14
Q
Mixture
A
- elements and compounds that are not chemically bonded
- can be separated by physical methods
- properties are the same as the properties of separate parts; no chemical properties are affected
15
Q
Chromatography
A
- used to separate out different dyes in an ink
1. Draw a pencil line at the bottom of a sheet of filter paper
2. Add a spot of ink and place in a beaker of solvent e.g. water
3. Solvent seeps up the paper (capillary action) carrying the ink with it
4. More soluble dyes travel further up the paper and vice versa, so they will separate out
5. End result is a series of spots, called a chromatogram
16
Q
Filtration
A
- used to separate insoluble solids from a liquid in a mixture
- also used in purification (removes solid impurities)
- uses filter paper and a funnel
17
Q
Evaporation / Crystallisation
A
- separating a soluble solid from a liquid in a mixture
- gently heat the mixture until the liquid has completely evaporated
- very quick method of separation
- leave in evaporating dish to evaporate naturally
- forms crystals (hence the name) of the solid
18
Q
Separating Rock Salt
A
- Grind the mixture to ensure it will dissolve easily
- Stir the mixture in water - salt will dissolve, but sand/rock won’t
- Filter the mixture. Grains of sand can’t pass through tiny holes in filter paper, so they will be left behind as residue
- Evaporate the water, until it leaves dry crystals of salt
19
Q
Simple Distillation
A
- Used to separate a liquid out of solution
- Solution is heated; lowest BP evaporates first
- Vapor is cooled, condensed and collected
- Rest of solution left behind in flask
- limitations: can only separate two liquids; both liquids must have very different BPs
20
Q
Fractional Distillation
A
- Heat solution with fractionating column on top
- Different BPs evaporate at different temperatures
- Lowest BP first; reaches top of column when thermometer reads its BP
- Column cooler towards top - higher BPs can’t reach top at this stage
- When first liquid collected, raise the temperature for the next liquid
e. g. separating crude oil
21
Q
Dalton’s model of the atom
A
- described atoms as solid spheres
- different spheres made up different elements
22
Q
Thomson’s model of the atom
A
- atoms aren’t solid spheres
- measurements of charge and mass show that atom must contain smaller, negatively-charged particles - electrons
- plum pudding model (ball of positive charge with electrons dotted around in it)
23
Q
Alpha particle scattering experiment
A
- Rutherford and student, Marsden
- particles should pass through or be slightly deflected
- some were deflected more than expected; a few deflected backwards
- devised nuclear model of the atom, key point being lots of empty space
24
Q
Rutherford’s model of the atom
A
- also known as nuclear model of the atom
- tiny, positively charged nucleus at centre, where most of mass concentrated
- ‘cloud’ of electrons surround nucleus; most of atom is empty space
25
Q
Bohr’s model of the atom
A
- elaboration for Rutherford’s nuclear model
- discovered that ‘cloud’ of electrons would collapse due to attraction to nucleus
- atoms must be contained in shells
- electrons orbit in fixed shells and aren’t anywhere in between
- ## each shell is a fixed distance from the nucleus
26
Q
Discovery of protons and neutrons
A
- Rutherford discovers protons
- further experiments, dividing hydrogen nucleus into smaller particles
- each smaller particle had same charge as hydrogen nucleus
- Chadwick discovers neutron
- experiments provide evidence for ‘neutral particle’
- almost same mass as proton, but no charge
