Atomic Structure + The Periodic Table Flashcards
What do atoms contain?
Electrons
Protons
Neutrons
What is the Nucleus?
- made of of a proton and a neutron
- positive charge
- centre of the atom
- almost all of the mass
What are the Relative masses and charges for Protons, Neutrons and Electrons?
Proton: 1, +1
Neutrons: 1, 0
Electrons: 0, -1
What is the electron?
- Revolve around the nucleus on electron shells
- negatively charged
- very small
- virtually no mass
What sub-atomic particle decided what type of atom an atom is?
The proton
- number of protons
What is an element?
a substance that only contains atoms all with the same number of protons
What are Isotopes?
A group of atoms with the same number of protons but a different number of neutrons
- different forms of the same element
What are Compounds?
Substances formed with two or more elements, held together by chemical bonds
- When elements react, atoms combine with other atoms
What is a Mixture?
2 or more elements or compounds that aren’t chemically bonded
- no chemical bond between different components in the mixture
How can mixtures be separated?
Physical methods
- filtration,
- crystallisation
- simple distillation
- fractional distillation
- chromatography
What are some examples of mixtures?
- Air
- Crude oil
What did John Dalton theorise about atoms at the Start of the 19th Century?
- atoms were solid spheres
- different spheres make up different elements
What did JJ Thompson conclude in 1897 about atoms?
- atoms weren’t solid spheres
- atoms contained a smaller negatively charged particle-> electron
- Plum Pudding Model- positive charged atom with negative electrons
What did Ernst Rutherford prove in 1909 about the atom?
- Alpha particle scattering experiments: Fired positively charged alpha particles at a thin sheet of gold
- some particles deflected more than expected, even backwards (disproved plum pudding model)
- Nuclear Model of the Atom
- tiny positive nucleus, cloud of negative electrons surround
- atoms are mostly empty space
What is an alpha particle?
The nucleus of a helium atom
What did Bohr discover about the nuclear model?
- Nuclear model of the atom-> electrons and positive nucleus would attract, atom would collapse
- Electrons were fixed on shells, orbiting at a fixed distance
What did Rutherford further discover AFTER Bohr’s electron shells?
- The nucleus can be divided into smaller particles, same charge as the hydrogen nucleus-> called Protons
Finally, what did James Chadwick discover about the atom?
20 years AFTER the discovery of the nuclei
- provided evidence of a neutral particle in the nucleus-> Neutrons
What is the order of the discoveries to do with the Atom?
John Dalton- Atoms
JJ Thompson- Electrons
Ernst Rutherford- Nucleus
Bohr- Electron Shells
Rutherford- Protons
James Chadwick- Neutrons
Where are the lowest energy levels located on the atom?
closest to the nucleus
- filled first
In the early 1800’s, how were Elements arranged?
By Atomic Weight
The other obvious way:
By Physical and Chemical properties
What was wrong with early periodic tables?
- Some elements were placed in the wrong group-> order of atomic weight
- The tables weren’t complete
What did Dmitri Mendeleev discover about the periodic table in 1869?
He took the 50 known elements and arranged them with gaps, predicting new elements
-Ordered them in atomic weight but moved some to take into account chemical properties
- Gaps left to make sure the right elements stayed with the right groups, predicting what was going to be in the gaps
How is the Modern Periodic table ordered?
- in increasing atomic number, thus repeating patterns of elemental properties
- can see which elements are metals and non-metals
- similar propertied form columns (groups)-> how many electrons in the outer shell
- ## rows-> periods, accounts for how many electron shells the atom has.
What is the trend of reactivity in Group 1?
The elements react more vigorously as you go down the group
What is the trend of reactivity in Group 7?
The elements become less reactive as you go down the group
What are Transition metals?
- typical metal properties
- can have more than 1 ion
- often coloured
- good catalysts
What are the properties of Group 1 elements?
- 1 electron in the outer shell, highly reactive
- soft, low density
- increasing reactivity as you go down
- lower melting and boiling points as you go down
- higher relative atomic mass
React with water-> vigorous, produce Hydrogen gas + metal hydroxides (alkali solutions)
- more energy released + more reactive as you go down
React with Chlorine-> vigorous, produce white metal chloride salts
- more vigorous as you go down
React with Oxygen-> form metal oxide (lithium oxide, sodium oxide or sodium peroxide)
What is the difference between Group 1 metals and the Transition metals?
Group 1 = much more reactive, more vigorous reaction
- less dense, strong hard
- lower melting points
What are the properties of Group 7 elements?
Halogens
All exist as diatomic molecules
- less reactive as they go down
- higher melting and boiling points as you go down
- higher relative atomic mass as you go down
Form ionic bonds with metals-> Halides
What are the coloured vapours of the Halogens?
Fluorine-> reactive, poisonous, yellow gas
Chlorine-> reactive, poisonous, dense green gas
Bromine- dense, poisonous red-brown volatile liquid
Iodine-> dark grey solid or purple vapour
What are the properties of Group 0 elements?
Noble gases
8 electrons in outer shell, fully reacted (helium has 2)
Inert- unreactive
Monatomic gases- single, not bonded
colourless at room temperature
non flammable
Boiling and melting points increase as you move down
Increasing relative atomic mass as you go down
