Atomic structure Flashcards
What is an atom?
The smallest part of an element that can exist + ALL substances are made up of atoms
What are chemical symbols?
Symbols (one or two letters) to represent an atom so it can universally recognised around the world
What is a compound?
A substance made up of two or more elements chemically joined together in fixed proportions
How are compounds formed?
From combining two or more elements by chemical reactions. Chemical reactions always involve the formation of one or more new substances + often involve energy change
How can compounds be separated?
By chemical reactions
What is a mixture?
They consist of two or more elements or compounds that ARE NOT chemically combined together. The chemical properties of each substance in the mixture are UNCHANGED
How can mixtures be separated?
- Filtration
- Crystallisation
- Simple distillation
- Fractional distillation
- Chromatography
What is chromatography?
A method used to separate and identify the components of a mixture of soluble substances
What is distillation?
A process used to separate liquids based on their boiling points
What is filtration?
A process used to separate liquids from insoluble solids
What is crystallisation?
A process of forming solid crystals from a solution by allowing the solvent to evaporate slowly
What is the atomic theory + who created it?
It was the theory created by the Greek philosopher, Democritus, which was that everything is made up from tiny particles that CANNOT be broken down any further + are separated from each other by empty space
What Russian scientist created the first successful periodic table?
Dmitri Mendeleev
What was John Dalton’s theory?
In 1803, he believed that he thought that all matter was made up of tiny particles called atoms, which he imagined as tiny solid spheres that couldn’t be divided
What was JJ Thomson’s ‘plum pudding model’?
He carried out experiments + discovered the electron. This led him to suggest the ‘plum pudding model’ - the atom is a ball of positive charge with negative electrons embedded in it
What was Ernest Rutherford’s experiment + ‘nuclear model’?
He 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 scattered in different directions.
This led him to suggest a new model for the atom which he called the ‘nuclear model’. In the nuclear model:
- The mass of the atom is concentrated in the centre, the nucleus
- The nucleus is positively charged
What was Niels Bohr’s model?
He adapted from Rutherford’s nuclear model + electrons orbit the nucleus in shells that were at a certain distance away from the nucleus
How were protons discovered?
Further experiments led to the idea that the nucleus contained small particles, called protons. Each proton has a small amount of positive charge.
What did James Chadwick discover?
He discovered the neutron was within the nucleus in 1932
What is the atomic number?
the number of protons (and electrons) in an atom of an element (the bottom number)
What is the same about atoms of the same element?
They have the same number of protons
What is the relative charge of protons, neutrons and electrons?
Protons = 1
Neutron = 0
Electron = -1
What is the number of protons equal to?
Number of protons = Number of electrons
How big are atoms?
0.1nm + the radius of a nucleus is less than 1/10,000 of that atom, though it holds almost all the mass
What is the mass number?
the total number of protons and neutrons in an atom (the top number)
What is the relative mass of protons, neutrons + electrons?
Protons = 1
Neutrons = 1
Electrons = 0
What are isotopes?
When atoms of the same element have different numbers of neutrons
What is the relative atomic mass?
An average value that takes account of the abundance of the isotopes of the element
How do you calculate the relative atomic mass?
(isotope 1 mass x abundance) + (isotope 2 mass x abundance) / 100
What does the electronic structure of an atom tell you?
How many electrons are in each shell
What is the maximum number of electrons in the first shell?
2
What is the maximum number of electrons that can be in the other shells?
8
