1. Atomic Structure And The Periodic Table Flashcards
(46 cards)
How can you separate a compound into elements?
With chemical reactions
How can you tell if a compound is a salt?
If it is a metal and a halogen - ends in ide
E.g. sodium chloride
How can you tell if a compound contains oxygen?
If it ends with -ate
E.g. sodium sulphate
Which elements are found as molecules?
iodine, I2
bromine, Br2
chlorine, Cl2
fluorine, F2
oxygen, O2
nitrogen, N2
hydrogen, H2
Can be remembered with:
I BRing CLay For Our New House
What is filtration?
Filtration is used to separate an insoluble solid from a liquid. It is useful for separating sand from a mixture of sand and water, or excess reactant from a reaction mixture.
Filtration works because the filter paper has tiny holes or pores in it. These are large enough to let small molecules and dissolved ions through, but not the much larger particles of undissolved solid.
How does crystallisation work?
Separates a soluble substance FROM a solvent
Crystallisation is used to produce solid crystals from a solution. When the solution is warmed, some of solvent evaporates leaving crystals behind. For example, crystallisation is used to obtain copper sulfate crystals from copper sulfate solution.
How does simple distillation work?
Separates a solvent FROM a solution
Simple distillation is used to separate a solvent from a solution. It is useful for producing pure water from seawater.
Simple distillation works because the dissolved solute has a much higher boiling point than the solvent. When the solution is heated, solvent vapour leaves the solution. It moves away and is cooled and condensed. The remaining solution becomes more concentrated as the amount of solvent in it decreases.
How does fractional distillation work?
Separates a mixture of substances according to their different boiling points
Fractional distillation is used to separate different liquids from a mixture of liquids. It is useful for separating ethanol from a mixture of ethanol and water, and for separating different fractions from crude oil.
Fractional distillation works because the different liquids have different boiling points. When the mixture is heated:
- vapours rise through a column which is hot at the bottom, and cooler at the top
- vapours condense when they reach a part of the column that is below the temperature of their boiling point
- each liquid is led away from the column
There are two ways of obtaining different liquids from the column:
- by collecting different liquids from different parts of the column - the substance with the lowest boiling point is collected at the top of the column
- by continuing to heat the mixture to increase the temperatures in the column - the substance with the lowest boiling point is collected first
What is the plum pudding model?
An idea that an atoms is a ball of positive charge with negative electrons embedded and the mass is evenly distributed - J J Thomson came up with this
What was the alpha particle scattering experiment?
Ernest Rutherford designed an experiment to test the plum pudding model. In the experiment, positively charged alpha particles were fired at thin gold foil. Most alpha particles went straight through the foil. But a few were scattered in different directions.
Explain the results of the alpha particle scattering experiment
- Most alpha particles pass straight through
- so most of the atom is empty space
- A few alpha particles deflected through large angles
- so mass is concentrated at the centre of the atom
- and nucleus is positively charged
Who discovered the nuclear model of the atom and what is it?
Ernest Rutherford as a result of the alpha particle scattering experiment said the atom is:
- mostly empty space
- the positive charge is all in the nucleus
- the mass is concentrated in the nucleus (opposite to plum pudding model)
- the electrons and nucleus are separate/electrons are in orbits (discovered by Niels Bohr)
When were neutrons discovered and by who?
What is the order of the discovery of the 3 subatomic particles?
James Chadwick, after electrons and protons
Order:
- Electrons
- Protons
- Neutrons
What is an isotope?
Different forms of the same element that contain equal numbers of protons but different number of neutrons in their nuclei
How do you calculate relative abundance?
Relative abundance = ((Percentage Abundance1 x Atomic Mass1) + (Percentage Abundance2 x Atomic Mass2)) / Total number of atoms
How do the number of electrons correlate to the periodic table?
All of the elements in the same group have the same number of electrons in their outer most shells (except group 0 - full outermost shell)
The number of electrons on the outermost shell corresponds to the group number
As you go down each period an electron shell is added
How many electrons are in each shell?
First shell: 2 electrons
Second and third shell: 8 electrons
Who was Dmitri Mendeleev and how did he arrange his periodic table?
He was a Russian chemist who devised the periodic table
He arranged the elements in order of increasing atomic weights but also took into account the properties of the elements and their compounds
This meant his table:
- Had gaps in it
- Showed elements with similar chemical properties lined up in groups
He also left gaps for unknown elements, and by looking at other elements, he could predict the properties of undiscovered elements
- e.g. he predicted ‘eka-silicon’ that would fit under silicone, which later was discovered to be germanium and its properties are similar to the ones Mendeleev predicted, confirming his table
From the atomic weights, some elements were in the wrong order as protons had not been discovered yet
- e.g. iodine and tellurium
- iodine has a lower atomic weight, so should’ve been placed before tellurium, but iodine has similar properties to chlorine and bromine, so Mendeleev swapped their positions
What does malleable mean?
Hammerable into different shapes
What does ductile mean?
Pullable into wires
What is an ion?
A charged atom
What does sonorous mean?
Capable of making a ringing noise
Describe the electronic structure of metals
- Tend to have 3 electrons or less in their outer shell
- In chemical reactions involving metals these electrons are given to another atoms
- When this happens the atom is called an ion
- The negative electrons are lost
- The protons stay the same so metals form positive ions
What are alkali metals?
The elements in group 1 which react with water to strongly form alkaline hydroxides
