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.
