Atoms, Bonding & Structures F4 Flashcards
Plum Pudding Model
- Thomson
- Electrons are dotted through a positively charged sphere.
Modern Model of Atom
- Rutherford
- Positive nucleus is orbited by electrons.
Who discovered neutron?
- Chadwick
- Neutral
Atom
Simplest part of element that can exist and take part in chemical reactions.
Element
Pure substance which contains only one type of atom.
Compound
Pure substance which contains two or more elements chemically combined.
Mixture
Substance which is not chemically combined and can be easily separated.
What does the number is electrons in outermost shell indicate?
Group number.
Isotopes
Atoms with the same atomic number but different mass number.
Ions
Charged particles formed when an atom either loses or gains electrons.
What are CATIONS?
Positively charged ions.
What are ANIONS?
Negatively charged ions.
What is the radius of an atom?
0.1nm
1nm =
= 1 x 10-9m
Radius of nucleus
1/10,000
Alloy
Mixture of 2 or more elements, at least one of which is a metal.
Has metallic properties.
What is steel an alloy of?
Iron and Carbon.
Bonding
How atoms / ions are held together
Structure
How atoms / ions are arranged
Metallic Structure
METALLIC BONDING Attraction between positive ions and delocalised electrons. - High melting and boiling points (attraction between positive ions and delocalised electrons) - Good conductors (delocalised electrons) - Malleable (can be hammered into shape) - Ductile (can be drawn into wire)
Giant Ionic Lattice Structure
IONIC BONDING
Ionic attraction between oppositely charged ions.
- High melting and boiling points
(substantial amount to break bonds of oppositely charged particles)
- Good conductors
- Soluble
SODIUM CHLORIDE
Molecular Covalent Structure
COVALENT BONDING (O2, H2O, NH3) - Strong covalente bonds - Low melting and boiling points (weak Van de Waals’ forces between molecules) - Don’t conduct (molecular covalent have neutral particles) - Insoluble
Giant Covalent Structure
COVALENT BONDING - 3D structure joined by covalent bonds - Large continuous networks of covalently bonded atoms • Diamond • Graphene • Graphite - All made of Carbon
Allotropes
Different forms of the same element in the same state.
Diamond
- Each carbon atom covalently bonded to 4 others
- Very hard due to strong covalent bonds
- Very high melting and boiling points because of covalent bonds
- Doesn’t conduct
(no free ions / delocalised electrons)
Graphite
- Most common form of Carbon
- Layers of Carbon atoms arranged in hexagons
- Weak Van de Waals’ forces between layers
- One electron per carbon atom is unbonded
(delocalised electrons) - Soft because layers can slide past each other due to weak Van de Waals’ forces
- Good conductors
(unbonded electron)
Graphene
- One atom thick layer
- Strong Covalent bond between each atom
- Very high melting and boiling points
(substantial energy) - Very strong due to strong covalent bonds
- Good conductor as one electron per carbon atom is unbonded
(delocalised electrons)
Ionic Bonding
- Metal & Non-Metals
- Electrons transfer from metal to non-metal
- Opposite charged ions attract to form large regular structures.
Covalent Bonding
- 2 or more non-metal atoms, sharing electron pairs
- Uncharged particles due to no ions
- Shared electrons attract nucleus of atom
Molecule
Two / more atoms covalently bonded together.
Diatomic
Two atoms covalently bonded in molecule.
Lone pair of electrons
2 / more unbonded electrons in molecules.
Metallic Bonding
- Attraction between positive metal ions in regular lattice and delocalised electrons
Delocalised electrons
Electrons that are free to move throughout the whole structure.
Covalent Bonds
One pair - SINGLE covalent
Two pairs - DOUBLE covalent
Three pairs - TRIPLE covalent
What is used in ALLOYS?
Gold
Silver
Copper
Zinc
How to find % of gold?
% = no. of carats/24 x 100
How to find amount of carats (K)?
K = % x 24 / 100
Nanoparticles
Structure that is 1-100nm in size and contain a few hundred atoms.
Surface Area to Volume Ratio
As the size of a cube increases, the surface area to volume ratio decreases.
Benefits of Nanoparticles
- Better skin coverage to sun cream
- More effective protection
- Clear and colourless
- Does not degrade on exposure to sun
Major Risks of Nanoparticles
- Harmful effects on humans & environment
- Potential cell damage in body
- More reactive / more toxic than bulk material
