Chem Test 31/March/25 2% 1st chem test Flashcards
(25 cards)
What is Atomic Absorption Spectrum? - (AAS)
Are analytical techniques that can be used to identify elements; these methods rely on electron transfer between atomic energy levels and are shown by emission line spectra
Atomic radius - Periods - across the periodic table trend. Explain-
Atomic radius/size DECREASES as you move from left to right.
Atomic radius - Groups - across the periodic table trend. Explain-
Atomic radius occurs as you move vertically down an element group. This direction increases the size of the atomic radius.
How to calculate RAM isotopes.
35CL ABUNDANCE-75.8%
17
N-37CL - 24.2%
P-17
A = [ (35 x 75.8) + (37 x 24.2) ] / 75.8 + 24.2
What is Relative Atomic Mass?
The relative atomic mass of an element is the weighted by the average of the masses of the isotopes on a
scale. E.g. A carbon-12 atom has a mass of exactly 12 units through neutrons.
Ionic bonding - what to know?
Forms positively and negatively charged ions in a crystalline lattice with electrostatic forces of attraction between oppositely charged ions
The ionic bonding properties of ionic compounds, including high melting point, brittleness and non-conductivity in the solid state
Ionic compounds conduct electricity when molten or in aqueous solution state which can be explained by the breaking of the bonds through polar nature of water in the lattice to give mobile ions
Metallic bonding - what to know?
Metallic bonding, arrangement of atoms with electrostatic forces of attraction between the nuclei of these atoms and their delocalised electrons that are able to move within the three dimensional lattice
The metallic bonding model can be used to explain the properties of metals, including malleability, thermal conductivity, generally high melting point and electrical conductivity.
Covalent bonding can be modelled as the sharing of pairs of electrons, resulting in electrostatic forces of attraction between the shared electrons and the nuclei of adjacent atoms
Covalent Molecular - what to know?
The properties of covalent molecular:
Include low melting point which can be explained by their structure and the weak intermolecular forces between molecules; their non-conductivity in the solid and liquid/molten states can be explained by the = “absence of mobile charged particles in their molecular structure”
Covalent network - what to know??
Properties of covalent network substances - include high melting point, hardness and electrical conductivity are explained by modelling covalent networks as three-dimensional structures that comprise covalently bonded atoms
Elemental carbon exists as a range of “Allotropes”, including graphite, diamond and fullerenes with significantly different structures and physical properties.
The glue for covalent molecular bonding
Intramolecular force between positively charged nucleus and electron field between the two elements
The glue for covalent network bonding
Positive charged nucleus and shared electron density have strong intramolecular forces. All atoms are covalently bonded to others in linked lattice; there are no separate or discrete units
Outline the absorption spectra
When light passes through an element, the element absorbs specific wavelengths, leaving dark lines in the spectrum.
Outline Emission Spectra
When an element is excited (heated or energized), it emits light at specific wavelengths, creating bright lines in the spectrum
Name factors that influence an elements absorption/emission spectrum (3)
- Electron energy levels
- Temperature
- Pressure
What is Mass Spectrometry
Is a technique used to identify and analyse molecules based on their mass and charge
Separation techniques by difference in particle size (1)
Sieving
Separation techniques by difference in BP and MP (3)
Vaporisation, distillation, fractional distillation
Separation techniques by density and solubility (1)
Immiscible liquids separate into two layers due to density
Separation technique by electrostatic attraction (2)
Magnetic-Nickel/cobalt
Electrostatic-Mineral sands containing zircon
5 Properties of metallic bonds
- Metals are lustrous (shiny)
- Metals are good conductors of electricity
- High Melting/Boiling points
- Malleable
- Ductile
5 Properties of ionic bonds
- High melting/boiling points
- Cannot conduct electricity
- Hard but brittle
- Poor conductors of heat
- Solid at room temperature
The glue for metallic bonding
Electrostatic attraction between the lattice of positively charged metal ions and ‘sea’ of delocalised electrons
The glue for ionic bonding
Electrostatic attraction between positive and negatively charged ions
3 Properties of covalent molecular bonding
- Low melting/boiling point
- Soft
- Poor conductors of electricity
