Atoms Flashcards
Compounds
- Chemically bonded
- Cannot be separated
Mixture
- Physically mixed
- Can be separated
Element
- Only possesses one type of atom
Law of Conservation of Mass
Law of conservation of mass states that mass is neither created or destroyed
Law of Conservation of Energy
Energy cannot be created or destroyed, only converted
A+B = AB
A + B is reactants
AB is product
Period
- Row
- Number of electron shells (shells with electrons in them)
- 7 periods in total
Group
- Column
- Number of electrons they’ve got in the outer shell
- Outer shell = valence shell
- 18 groups in total
- 8 main groups
Charges
- If electrons are collected, a charge is given
- If there is a charge it is an ion
- If there is a positive charge it is a cation
- If there is a negative charge it is an anion
- If an electron is gained it has a - ion
- If an electron is lost it has a + ion
Metals
- Positive charge (cation)
- Loses electrons
Non-metals
- Negative charge (anion)
- Gains electrons
Ionic Bonding
- Positive and negative (metals and non-metals)
- Ionic bonds dissolve in water
- When ionic bonds dissolve in water, the water particles prevent the ions from sticking back together
The ions are then spread evenly throughout the water to create a solution - Electrons move to and from one another
- To balance electron numbers in outer shell
Balancing compounds
Li2O
Lithium = needs to lose 1 electron (non metal)
Oxygen = needs 2 electrons (metal)
Therefore, two lithium are needed to balance oxygen and lithium
Covalent bonding
- Negative and negative
- Only share electrons from outer shell
- When sharing, electrons move back and forth between elements
- Nonmetals and nonmetals join together
Covalent Bonding Example
E.g. H2O
- Hydrogen needs 1 electron (for a full outer shell) and
- Oxygen needs 2 electrons (for a full outer shell)
- H2O - there are 2 hydrogen atoms (1 more electron)
- The hydrogen atoms share their electrons to the oxygen atom to make a full outer shell (in the oxygen atom)
- The oxygen atom shares 2 of its electrons to the hydrogen atom to make a full outer shell (in the hydrogen atoms)
Noble Gasses
- Outer shell is full
- Is inert so does not give, take, share electrons
- 18th (8th) group of the periodic table
2n^2
- The formula for the maximum number of electrons the shell can hold
- N = the shell number
- 2(1)^2 = 2 - the first electron shell can hold 2 electrons
- 2 (2)^2 = 8 - the second electron shell can hold 8 electrons
- Shell number^2, then times 2
Electron Configuration
- Written format for number of electrons in each shell
- Beryllium (4 electrons) = 2,2
- Oxygen (8 electrons) = 2,6
Ionic Formulas
- Write the valence (number electrons in outer shell to gain or lose)
Fe3+ (needs to lose three electrons), O2- (needs to gain 2 electrons)
- Cross the valences
Fe = 2-
O = 3+ - Drop the +/-
Fe = 2
O = 3
Ionic Formula:
Fe2O3
- Reduce if possible
Fe2 means number of atoms - how many elements needed to balance
Fe^3+ means number of electrons to lose or gain (determined by -/+)
Mass Number
The total amount of protons + neutrons
- Number at the top left or bottom (in periodic table)
Atomic Number
Number of protons
- Number of protons is equal to number of electrons
- Number at the top left (in periodic table) or bottom left
electron vs proton mass
An electron’s mass = 1/1800 of a protons mass
Shell energy
- Each shell has a different level of energy
- Increases as shell number grows
- Put heat to ‘excite’ electron = more energy
- With more energy, the electron will jump to an electron shell that is further away from the nucleus
- After cooling, energy will change form
E.g. Fireworks, fire excites electron as ascending, electron cools and changes to the form of light energy
The heat will change into kinetic energy and into light when it cools down
Polyatomic Ion
A polyatomic ion is an ion comprised of two or more atoms and have an overall charge
- When 2 capitals are next to each other
E.g.
Hydroxide anion (OH-)
Phosphate anion (PO43-)
Ammonium (NH4+)
Writing equations
When writing equations, metals are always written first
