Atomic Structure + Periodic Table Flashcards
Arrangement of periodic table
- elements arranged in order of atomic number and so elements of similar properties are in columns (groups)
- elements in the same group have the same amount of electrons in their outer shell-gives them similar chemical properties
Relative atomic mass
protons +neutrons, bigger number
Atomic number
number of protons, smaller number
John Newlands ( early periodic table )
- ordered his table in order of atomic weight
- realised similar properties occurred every eighth element
-‘law of octaves’ but broke down after calcium
Dmitri Mendeleev (early periodic table)
-ordered his table in order of atomic mass, but not always strictly (in some places he changed order based on atomic weights)
-left gaps for elements that he thought had not been discovered
Why was order based on atomic weights not always correct?
Knowledge of isotopes
Reactivity of group 1 (alkali metals)
- all react with oxygen to create an oxide
- all react with chlorine to form a white precipitate
- reactivity of elements increases going DOWN the group
- react vigorously with water to create an alkaline solution and hydrogen
Reactivity of Group 0 (noble gases)
-full outer shells
-unreactive and don’t easily form molecules because they have a stable arrangement of electrons
-boiling points of noble gases increase going down the group
Reactivity of group 7 (halogens)
-non-metals
-exist as molecules (Cl2)
-react with metals to form ionic compounds
-react with non metals to form covalent compounds
How did John Dalton think atoms were formed
-solid spheres
-different spheres made up different elements
What did J J Thompson think about the atom
-concluded atoms weren’t solid spheres
-believed atoms must contain negatively charged particles:electrons
-this theory was the plum pudding model
-was shown as a ball of positive charged particles with electrons stuck in it
Who created idea of plum pudding model
J J Thompson
Who did alpha particle scattering experiment
Ernest Rutherford
What was expected to happen in alpha particle scattering experiment
-expected particles to pass straight through because the positive charge of the atom was believed to be very spread out
What actually happened in alpha particle experiment
-most particles went straight through the gold sheet
-more were deflected than expected and some were deflected backwards
Who came up with idea of nuclear model
Rutherford first, then Bohr
What is Rutherford’s nuclear model
-tiny positively charged nucleus as centre where most of the mass is concentrated
-a ‘cloud’ of negative electrons surround nucleus
-so most of the atom is empty space
What is Niels Bohr’s nuclear model
-electrons were contained in shells
-electrons orbit the nucleus in fixed shells and at a fixed distance
Who discovered protons and what happened
-Rutherford
-experiments showed that the nucleus could be divided into smaller particles
-same charge as hydrogen nucleus, called protons
What did James Chadwick discover
-carried out experiment which provided evidence for neutral particles in nucleus
-now called neutrons
Who discovered neutrons
James Chadwick
Properties of metals
-all have metallic bonding
-strong
-malleable (can be bent or hammered)
-conduct heat+electricity
-high melting+boiling points
Properties of non-metals
-dull looking
-more brittle
-aren’t always solid at room temp
-don’t usually conduct electricity
-lower density
Reaction of group 1 elements with water
-produces hydrogen gas
-react vigorously
-the lower down in the group, the more vigorous
