Key concepts Flashcards
Topic 1
What is covalent bonding
When atoms share pairs of electrons
What is covalent bonding between
Two non-metallic elements
what is a simple molecular compound
are substances composed of molecules held together by covalent bonds
properties of a simple molecular compound (boiling point melting point)
low boiling and melting points
Structure of a simple molecular compounds in 4 points
-Non-metal elements
-Held together by covalent bonds
-With weak intermolecular forces
- Low boiling/ melting points
-Many insoluble in water
Can simple molecular structures conduct electricity, why?
no, small molecules aren’t big enough to be able to carry a charge
How are ionic bonds formed
Metal + Non-metal
metals lose an electron: become positive
non-metals gain an electron: become negative
What is an ion
an atom which a charge (either positive or negative)
What does the suffix ‘-ide’ mean
a compound containing 2 elements
What does the suffix ‘-ate’ mean
a compound containing 3 elements
What’s the formulae of Oxide
O (-2 ion)
What’s the formulae of Hydroxide
OH (-1 ion)
What’s the formulae of Halide
-1 halide
What’s the formulae of Nitrate
NO3 (-1 ion)
What’s the formulae of Carbonate
CO3 (-2 ion)
What’s the formulae of Sulphate
SO4 (-2 ion)
Describe the structure of an Ionic Lattice in 4 points
- a giant structure of ions
- held together by large electrostatic forces
- Between oppositely charged ions
- In a regular arrangement
Describe the properties of ions (melting and boiling point)
High melting points, High boiling points
Can ions conduct electricity, why?
Yes when molten or liquid as they have delocalised electrons that can carry a charge
No when solid
What do ions form when dissolved
An aqueous solution
How did Mendeleev organise the periodic table
- Order of atomic mass (sometimes weight)
- Left gaps for unknown elements
How did Mendeleev predict the existence of unknown elements
Realised groups with similar properties should be in the same group
What is a period
a row of chemical elements.
(horizontal)
What is a group
a column of chemical elements
(vertical)
What is the commonality within groups on the periodic table
Tells you how many electrons upon the outermost shell
What is the commonality within periods in the periodic table
show the number of shells of electrons
How is the periodic table arranged
- vertical columns based on their properties and the properties of their compounds
- horizontally in order of increasing atomic mass
How many electrons can an electron hold on it’s first fixed shell
2
What is the outmost electron shell called
Valence shell
Why did the Dalton model of the atom change over time?
Sub-atomic particles were discovered
What was the Dalton model
- all matter is made of atoms, which are indivisible.
- all atoms of a given element are identical in mass and properties.
What did J.J Thompson discover and how
Electrons
* used a cathode-ray tube proving atoms as divisible
What model did Thompson devise
The plum pudding model
* a negatively charged electrons
* positive-charged soup
What did Ernest Rutherford discover and how
The nucleus
* gold foil experiment
What was the gold foil experiment
- Shot a beam of positively charged particles into a sheet of gold
- Most of the particles did continue in a straight line while some deflected/bounced back
What model did Ernest Rutherford discover
The nuclear model
* consists of empty space with a nucleus in the middle
* electrons orbit the nucleus
What is the Bohr Model
- electrons orbit the nucleus in fixed shells
Proton
Relative charge:
Relative mass:
Relative charge: +1
Relative mass: 1
Neutron
Relative charge:
Relative mass:
Relative charge: 0
Relative mass: 1
Electron
Relative charge:
Relative mass:
Relative charge: -1
Relative mass: 1/1836
Why do atoms contain equal number of protons and electrons
Atoms are neutral
Protons = +1
Electrons = -1
same amount cancel out
What is the mass number of an atom
no* of protons + no* of neutrons
What is the atomic number of an atom (proton number)
amount of protons (and electrons)
How to work out the number of neutrons
mass no- atomic no
What is an isotope
elements with the same number of protons but different number of neutrons
Why are some relative atomic masses not whole numbers
isotopes have different masses, the relative atomic mass of an element is calculated by the weighted average of the masses.
How do you calculate R.A.M
(relative atomic mass)
(mass of isotope-A x % of isotope-A) + (mass of isotope-B x % of isotope-B) ÷100
