Flashcards in Atomic Structure And The Periodic Table Deck (41):
What was Rutherford's nuclear model of the atom?
There is a tiny, positively charged nucleus at the centre, where most of the mass is concentrated. A 'cloud' of negative electrons surrounds the nucleus - so most of the atom is empty space. When alpha particles came near the concentrated, positively charge of the nucleus, they were deflected. If they were fired directly at the nucleus, they were deflected backwards. Otherwise, they passed through the empty space.
Ways to separate mixtures
- simple distillation
- fractional distillation
How big is an Atom's radius?
0.1 Nanometers (1x10^-10m)
What did James Chadwick find?
He provided evidence for neutral particles in the nucleus which are now called neutrons.
What did Mendeleev do in 1869?
He took 50 known elements and arranged them into his own table of elements. He put them mainly in order of atomic mass but did switch that order if the properties should be changed.
What is an ion?
And ion is an atom or a group of atoms that have lost or gained electrons
What do atoms contain?
Protons, Neutrons and Electrons
- have metallic bonding
- they're strong
- can be bent into different shapes
- can conduct heat and electricity
- high boiling and melting points
- alkali metals
- low density
- react with water
- produce hydrogen
- form hydroxides that dissolve in water
What decides what type of atom it is?
The number of protons in the nucleus
What did Rutherford find?
He found that most of the particles did go straight through the gold sheet and some were deflected more than expected, and small number where deflected backwards.
The same number of protons and electrons
What did Bohr's nuclear model suggest?
All the electrons where contained in shells
- less reactive as you go down
- highs melting and boiling points as you go down
- have higher relative atomic masses as you go down
Neutral (no charge)
What does the mass number tell us?
The number of protons and neutrons there are in an atom
What are isotopes?
Isotopes are different forms of the same element that has the same number of protons but different number of neutrons (same Atomic number and different Mass number)
What did JJ Thomson conclude in 1897?
Atoms weren't solid spheres. His measurements of charge and mass showed an atom must contain even smaller, negatively charged particles - electrons. He 'solid sphere' idea of atomic structure had to be changed. The new theory was known as the 'plum pudding model'
What does 2- mean?
2 more electrons than protons
What is ionic bonding?
The opposite charges of the ion means they are strongly attracted to each other
- don't have metallic bonding
- dull looking
- aren't always solids at room temperature
- don't conduct electricity
- lower density
What did John dalton describe atoms as in the 19th century?
Solid spheres. He said that different spheres made up different elements
It tells us how many electrons are in its outer shell. E.g group seven all have 7 electrons in their outer shell.
What is the plum pudding model?
It showed the atom as a ball of positive charge with electrons stuck on it.
How do you find the number of neutrons?
Mass number - atomic number
- move around the nucleus in electron shells
- negatively charged and tiny, but they cover a lot of space
- the volume of their orbits determines the size of the atom
- have virtually no mass
What did Ernest Rutherford do in 1909?
He concluded the famous alpha particle scattering experiments. He fired positively charged alpha particles at an extremely thin sheet of gold.
What is covalent bonding?
Each atom shares an electron with another atom
How are compounds formed?
When elements react, atoms combine with other atoms to form compounds
How do you workout the relative atomic mass?
Sum of (isotope abundance x isotope mass number) divided by sum of abundances of all the isotopes
What does the atomic number tell us?
How many protons there are
- middle part of the atom
- contains protons and neutrons
- radius of 1x10^-14m)
- positive charge because of the protons
The Metal atoms...
Lose electrons to form positive ions.
What did Rutherford show after Bohr?
That the nucleus can be divided into smaller particles, which have the same charge as a hydrogen nucleus. These particles were named protons.
- noble gases
- don't react with much
- they exist as monatomic gases (single atoms not bonded together)
- boiling points increase as you go down
How are compounds held together?
What is an element?
It is a substance made up of atoms that all have the same number of protons in their nucleus
1st shell: 2
2nd shell: 8
3rd shell: 8
In an ion...
The number of protons doesn't equal the number of electrons. This means it has an overall charge
Why do protons and electrons cancel out?
Because they have the same charge but opposite (protons are positively charged and electrons are negatively charged)