Atomic Structure and the Periodic Table Flashcards
What is an atom?
The smallest part of an element that can exist.
What is an element?
A substance made up of atoms that all have the same atomic number/number of protons in their nucleus.
What is a compound?
2 or more elements chemically bonded together.
What is a mixture?
2 or more elements or compounds not chemically combined together.
e.g. air
Give 5 chemical formulas for compounds and identify how many elements/atoms they contain.
› Carbon Dioxide - CO₂ = 1 carbon atom, 2 oxygen atoms.
› Ammonia - NH₃ = 1 nitrogen atom, 3 hydrogen atoms.
› Water - H₂O = 2 hydrogen atoms, 1 oxygen atom.
› Sodium Chloride - NaCl = 1 sodium atom, 1 chlorine atom.
› Carbon Monoxide - CO = 1 carbon atom, 1 oxygen atom.
› Hydrochloric Acid - HCl = 1 hydrogen atom, 1 chlorine atom.
› Calcium Chloride - CaCl₂ = 1 calcium atom, 2 chlorine atoms.
› Sodium Carbonate - Na₂CO₃ = 2 sodium atoms, 1 carbon atom, 3 oxygen atoms.
› Sulfuric Acid - H₂SO₄ = 2 hydrogen atoms, 1 sodium atom, 4 oxygen atoms.
Practice balancing equations.
Practice balancing equation.
How can filtration be used to separate mixtures?
To separate insoluble solids from liquids and solutions, also can be used for purification as well.
How can crystallisation be used to separate mixtures?
- Pour the solution into an evaporating dish and gently heat the solution which will evaporate some of the solvent and the solution will get more concentrated.
- When you see crystals start to form, remove the dish from the heat and leave the solution to cool.
- The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution.
- Filter the crystals out of the solution and leave them in a warm place to dry.
How can simple distillation be used to separate mixtures?
Distillation is used to separate mixtures which contain liquids.
- Solution is heated and the part of the solution with the lowest boiling point evaporates first.
- The vapour is then cooled which then condenses and is collected.
- The rest of the solution is left in the flask.
How can chromatography be used to separate mixtures?
This is used to separate compounds out of a mixture.
- Draw a line with pencil 1-2cm away from the bottom a filter paper.
- Add a spot of ink to the line and place sheet in beaker of solvent (make sure ink isn’t touching solvent).
- Place a lid on top of the container to stop the solvent evaporating.
- The solvent seeps up the water carrying the ink with it.
- Different dyes will move up the paper at different rates and when it reaches the top of the paper, take the paper out of the beaker to dry.
What is the formulae to finding the R𝚏 value?
distant travelled by substance / distance traveled by solvent.
What did Rutherford say about the atom?
He was the third to speak on atoms saying that the plum pudding was wrong. He thinks that the nucleus is positively charged which is where the mass is concentrated and a ‘cloud’ of negative electrons surround this nucleus so most of the atom is empty space.
What did Neils Bohr say about the atom?
He was the last one to speak on atoms making the nucleus model of the atom which suggested that all electrons were contained in shells. The electrons orbit the nucleus in fixed shells and aren’t anywhere in-between as each shell is a fixed distance from the nucleus.
What did John Dalton say about the atom?
He was the first to speak on atoms. At the start of the 19th century, he said that atoms are solid spheres and that the different spheres made up different elements.
What did JJ Thompson say about the atom?
He was the second one to speak on atoms in 1897 saying that atoms aren’t solid spheres as his measurements of charge and mass showed that atoms must contain even smaller, negatively charged particles such as electrons which was called the plum pudding model. It shows that the atom is a ball of positive charge with negative electrons embedded on it.
Describe a nucleus.
›it’s in the middle of the atom.
› contains protons and neutrons.
› positively charged because of protons.
› mass of atom concentrated in the nucleus.
Describe an electron.
› move around the nucleus in electron shells.
›negatively charged and tiny but cover up a lot of space.
› volume of their orbit determines the size of atom.
›no mass.
What is a protons relative mass and relative charge?
RELATIVE MASS: 1
RELATIVE CHARGE: +1
What is a neutron relative mass and relative charge?
RELATIVE MASS: 1
RELATIVE CHARGE: 0
What is an electron relative mass and relative charge?
RELATIVE MASS: very small.
RELATIVE CHARGE: -1
What does the atomic number tell you?
The amount of protons (bottom number).
What does the mass number tell you?
Total number of protons and neutrons (top number).
How do you find the amount of neutrons?
mass number - atomic number.
Why do atoms have no overall electrical charge?
They have the same number of protons as electrons.
What are isotopes?
Atoms which have the same number of protons but a different number of neutrons.
What is meant by the term relative atomic mass?
An average mass number for an element.
[Aᵣ = sum of (isotope abundance x isotope mass number) / total abundance of all isotopes]
How are elements arranged in the periodic table?
In order of atomic number (protons).