C1: Atoms Flashcards
What is an element?
A substance containing only one type of atom
What is a compound?
A substance containing two or more different types of atoms CHEMICALLY BONDED
What is the conservation of mass?
Atoms can neither be created or destroyed in a reaction - equations must be BALANCED
What is a mixture?
Consists of different substances NOT CHEMICALLY BONDED
What does filtration do?
Removes large, insoluble particles from a liquid
How does evaporation separate substances?
Leaves behind crystals of a dissolved substance (solute) if heated gently
What does distillation involve?
Condensing the evaporated solvent and collecting it
What can fractional distillation do?
Separate liquids due to their different boiling points
What are characteristics of a solid?
- Arranged in a regular lattice
- Vibrate about fixed positions
- Cannot be compressed
What are characteristics of a liquid?
- Particles have no regular arrangement
- Able to move past each other
- Cannot be compressed
What are characteristics of a gas?
-Particles are far apart
- Move randomly at fast speeds
-Can be compressed
How does heat cause melting/evaporation?
The energy overcomes the electrostatic forces of attraction
Physical change
What are the different state symbols?
Solid = s
Liquid = l
Gas = g
Substance in a solution is aqueous = aq
How does chromatography work?
Causes substance to rise up paper due to capillary action. Lighter particles move further up
What did ancient Greeks believe matter was made up of?
Invisible particles
What was JJ Thomson’s atomic model?
-Plum pudding model
-Cloud of positive charge with negative electrons dotted in it
What did Ernest Rutherford discover?
-The nucleus was small and positively charged
-Alpha scattering
-Most alpha particles went through gold leaf, very few reflected back
What did Neil’s Bohr discover?
Electrons exist in shells
What did James Chadwick determine?
The nucleus must contain neutrons as well as protons
What is the relative mass and charge of a proton?
Relative mass = 1
Relative charge = +1
What is the relative mass and charge of a neutron?
Relative mass = 1
Relative charge = 0
What is the relative mass and charge of an electron?
Relative mass = almost 0
Relative charge = -1
What is the atomic number?
-The number of protons in a nucleus
-Bottom number
-Also tells us number of electrons if neutral
What is an ion?
-A charged atom
-Has a different number of electrons
What is the mass number?
-The number of protons + neutrons in a nucleus
-Top number
What are isotopes?
Same element, different numbers of neutrons
What is the relative abundance of chlorine 35 & 37?
Chlorine-35 = 75%
Chlorine-37 = 25%
How do you work out average relative atomic mass?
Average mass = total mass of 100 atoms / 100
How were elements initially ordered?
-According to their ATOMIC ‘WEIGHT’
-Some grouped together due to having SIMILAR PROPERTIES
What did Dimitri Mendeleev do?
-Left gaps in table for predicted elements
How many electrons can be on the first, second and third shells?
First = 2
Second = 8
Third = 8
What do metals do to gain an empty outer shell?
Donate electrons to form positive ions
What do non-metals do to gain a full outer shell?
Accept electrons to form negative ions
Can also share electrons
What do groups tell us?
The number of electrons in the outer shell
What are atoms in group 1 called?
The alkali metals
What are characteristics of group 1 metals?
-Ions are all (1)+
-React with water to produce an alkali
-Get more reactive down the group
Why do metals become more reactive down the group?
-The outer electron is further from the nucleus
-Donated more readily as the force of attraction is less
What are atoms in group 7 called?
The halogens
What are characteristics of group 7 atoms?
-Ions are all (1)-
-Become less reactive down the group
-Boiling point increases down the group
Why do group 7 atoms become less reactive down the group?
-The outer shell is further from the nucleus
-The electrostatic force between the nucleus and the outer shell is weaker
Why are noble gases (group 8) very unreactive?
They already have an empty/full outer shell
Why can you get different ions of transition metale.g. Iron (II), Iron (III)?
They can donate different numbers of electrons
