Chemistry Term 1.1-1.3

Nature of matter, Seperation methods, structure of an atom, isotopes, electron configuration, line spectra, hydrogen emission spectra, main energy levels and sublevels,

What can a matter be divided into?

Pure substances (compounds, elements), mixtures

what is a compound

two or more elements chemically bonded, fixed ratio

what is a element

1 type of atom, simplest form of an element, cant be broken down into anything simpler

what is a mixture

two or more different elements or compounds, not fixed ratio, either heterogenous or homogenous

what is a heterogenous mixture

non-uniform composition, visible layers

what is a homogenous mixture

uniform composition, non-visible layers

what are the different states of matter

gas, liquid, solid

factors of a gas

far apart, random, move quick in all directions

factors of a liquid

close together, random arrangement, move around each other

factors of a solid

close together, vibrate, regular pattern

what are the different changes of state

chemical change, physical change

what is a chemical change

making a new substance

what is a physical change

rearranging of particles

example of a physical change

ice (solid) → water (liquid) → steam (gas)

solid → liquid

meliting

liquid → gas

vaporization

gas → liquid

condensation

liquid → solid

freezing

solid → gas

sublimation (adding heat (endothermic))

gas → solid

deposition (remove heat (exothermic))

different separation methods

filtration, distillation, paper chromatography, solvation

what is filtration

separating particles based on size using a porous material (the filter)

what is distillation

separating particles by different boiling points

what is paper chromatography

separating particles by their different affinities

what are the phases in paper chromatography

mobile phase (solvent moves up the paper), stationary phase (paper)

what is solvation

separating particles based on their solubility in different solvents

what is a solvent

water or alcohol

example of solvation

adding salt to water

what are radioisotopes

unstable radioactive isotopes due to the number of subatomic particles (protons or neutrons) in the nucleus

what are radioactive isotopes

substance that has an unstable nuclei, emits radiation as it decays

subatomic particles

electrons, neutrons, protones

factors of the nucleus

very dense, positively charged, contains almost the whole mass of the atom

how much does the nucleus weigh

= 2.3 × 10^17 kg m-3

electron symbol

e^-

electron relative charge

-1

electron relative mass

1/2000

proton symbol

p⁺

neutron symbol

n⁰

proton relative charge

+1

neutron relative charge

0

proton relative mass

1

neutron relative mass

1

what are ions

an atom that has either lost or gained an electron

what are positive ions

when atoms lose electrons

what are negative ions

when atoms gain electrons

example of positive ion

sodium loses 1 electron to form a 1+ ion

example of negative ion

fluorine can gain one electron to form a 1- ion

what is a isotope

atom of same element with different number of neutrons

what changes do isotopes have

isotopes of same element behave similarly in chemical reactions, different physical properties cause if the masses

how to calculate relative atomic mass, Ar

from the percent abundance and masses of the isotopes of the atime

what is percent abundance

percent of an isotope in a naturally occurring sample of an elements

calculation of Ar with percent abundance

mass of each isotope is multiplied by its percent abundance, these values are added together and then divided by 100

hydrogen isotopes

hydrogen -1 (mass # 1), hydrogen -2 (deuterium (mass # 2)), hydrogen -3 (tritium (mass # 3))

how many regions is the electromagnetic spectrum divided into

1-7 regions, low energy → high energy (radio waves → gamma rays)

realtionship between energy, frequency and wavelength

high energy = high frequency = low wavelength (vice versa)

how is an emission line spectra formed

when electrons transition from high → low energy levels

what do electrons emit when transitioning from high → low energy levels

emit energy

what does ele. tran. to n=3 emit

infrared radiation

what does ele. tran. to n=2 emit

visible light

what does ele. tran. to n=1 emit

ultraviolet radiation

what does an emission line spectra show

specific wavelengths or frequencies of electromagnetic radiation (colours)

what is a continous spectrum

shows all wavelengths or frequencies of visible light

at what speed do the 7 regions travel at

speed of light → 3 × 10⁸ m s ^-1

what is the continuous spectrum produced by

• hot liquids

• hot gas under pressure or plasma from sun

• hot solids (glowing filament in an incandescent globe)

what happens to the lines on an emission spectra

converg (closer together) at high energy (high frequency, low wavelength)

how can electrons move between energy levels

• absorbing energy

• emitting energy

The form of energy absorbed or emitted is in photons

what happens if ele. absorb energy

transition from low energy → high energy

e.g. n=2 → n=3

what state do electrons go in when they transition to a higher energy level

‘excited state’

what is the ‘excited state’

unstable relative to ground state (n=1)

• once ele. go to excited state they are unstable and go back to n=2

what does it mean if more energy is emitted (in terms of energy levels)

bigger jump in ‘n levels’

• n=2 → n=5 more energy than n=2 → n=3

what is the absorption spectra

opposite of an emission spectra

what evidence does the hydrogen emission spectrum provide

• provides evidence for energy levels in atom

what do the lines of an hydrogen emission spectrum represent

each line represents a discrete energy level in the hydrogen atom

• electrons can only occupy these energy levels

what does n=∞ refer to

refers to point when ele. has been completely removed from attraction of nucleus

• and atom has been ionised

where are electrons located

discrete energy levels:

• main energy levels

• principle energy levels

what are atomic orbitals

a region of space we assign because we never really know where ele. are located

what are main energy levels divided into

sublevels

different types of sublevels

s, p, d and f (based on shape of atomic orbitals they contain)

factors of an s atomic orbital

• spherical

• maximum 2 electrons

• only has a single s atomic orbital

factors of p atomic orbitals

• dumbbell shape

• maximum 6 electrons

• 3 p atomic orbitals

factors of f atomic orbital

• 7 atomic orbitals

factors of d atomic orbital

• 5 d atomic orbitals

how many electrons can a single orbital hold

maximum 2 electrons

formula to find the # of orbital at each major energy level

n² = # of orbital at each major energy level

what is the aufbau principle

when adding electrons to atom, lower energy orbitals must be filled first

what is the Pauli exclusion principle

atomic orbitals can only hold 2 electrons

• must have opposite spins

what is Hund’s rule

when we have degenerate orbitals, each orbital gets 1 electron before being doubly occupied

what are degenerate orbitals

orbitals of same energy → e.g. three 3p orbitals

what are the core elements and their symbol

[He] = 1s²

[Ne] = 1s²2s²2p⁶

[Ar] = 1s²2s²2p⁶3s²3p⁶

Rules of electron configuration (subatomic particle blah blah)

overlap of energy between the 3d and 4s sublevels

• ele. are removed from 4s sublevel first when forming ions

Aufbau principle exceptions

• copper (Cu)

  • [Ar]4s¹ 3d¹⁰

• chromium (Cr)

  • [Ar]4s¹ 3d⁵