Recipe book of the Universe Flashcards
Solar system definition
Gravitationally bound system of the sun and the objects that orbit around it
Galaxy
Huge collection of gas dust, billions of stars and their solar systems, held together by gravity
Star
Large, spherical celestial body consisting of a mass of gas that is hot enough to system nuclear fusion, thus producing radiant energy
Nebulae
Cloud of gas and dust in outer space, visible in night sky as an indistinct bright patch or as a dark silhouette against other luminous matter.
Relate colours of stars to their age
- Younger stars: Blue, brighter, heavier, bigger, hotter
- Older stars: Red, less bright, lightest, smaller, less hot
- Older stars reduce the energy they emit as they run out of hydrogen
Electron description
- Negative charge
- Located in energy shells around nucleus
- Responsible for reactivity
Neutrons description
- Neutral charge
- Located in nucleus
- Holds together nucleus
Protons description
- Positive charge
- Located inside nucleus
- Determines atom identity
What does the atomic number represent?
Amount of protons
What is the chemical symbol?
The shortened version of an element’s name
What is the atomic mass?
Approximately equivalent to number of protons and neutrons in an atom
Group meaning
How many electrons are on the valence shell of an atom, displayed vertically on the periodic table
Period meaning
Number of electron shells an atom has, displayed horizontally on the periodic table
General properties of elements on left side of periodic table (group 1 and 2)
- Low melting points
- Highly reactive
- Malleable, solid metals
General properties of elements on right side of periodic table (group 7 and 8)
- Low boiling points
- Highly reactive (except noble gases)
- Non-metals
Features of Alkali metals (Group 1)
- High thermal and electrical conductivity
- Shiny lustre
- Ductile, malleable, soft
- Low melting and boiling points
- Very high reactivity
Features of Alkaline earth metals (Group 2)
- good electrical conductivity
- shiny lustre
- low density, melting, and boiling points
- somewhat reactive
Features of Halogens (Group 7)
- low melting and boiling points
- fairly toxic
- includes gases, liquids, and solids
- salt producing
- highly reactive
Features of Noble gases (Group 8)
- non-flammable
- colourless, odourless
- gases at room temp
- low boiling temps
- non-reactive/stable
Johann Dobereiner’s periodic table design (1817)
- Organised elements intro triads based on chemical properties
John Newlands’ periodic table design (1864)
- Arranged elements in increasing order of atomic mass
- Law of octaves: found that every 8 elements had similar chemical properties
- Arranged elements in 8 groups
- Didn’t leave room for undiscovered elements
Dmitri Mendeleev’s periodic table design (1869)
- Wrote symbols for the chemical elements
- Put them in order in increasing atomic mass
- Left gaps in table for undiscovered elements
- Correctly predicted properties of the missing elements
Henry Moseley’s periodic table design (1931)
- Arranged elements according to atomic numbers
- Indicated identity of an element is how many protons it has
Democritus atomic theory (460 BC)
- First formation of atomic theory
- Smallest possible bit of matter
- Indivisible particle everything made up of
John Dalton atomic theory (1800)
5 atom laws:
- Everything made of atoms: indivisible building blocks of matter which cannot be destroyed
- All atoms of an element are identical
- Atoms of different elements vary in size and mass
- Compounds produced through different whole-number combinations of atoms
- Chemical reactions result in the rearrangement of atoms in reactant and product
JJ Thompson atomic theory (1897)
- Plum pudding model
- Discovered electrons/negatively charged particles
- Cathode ray experiment
- passing electric current through cathode ray tubes
- discovered cathode rays were beams of negatively charged particles because ray bent towards positively charged plate
Ernest Rutherford atomic theory (1911)
- discovered nucleus (tiny, dense, positively charged core)
- discovered most of atom was empty space
- fired alpha particles at thin sheets of gold foil
- some particles deflected wildly in one direction or another
- he thought they would pass straight through
Neil’s Bohr Atomic theory (1913)
- Proposed stable electron orbits, explained the emission of spectra at some elements.
