Topic 1 - Atomic Structure And Periodic Table Flashcards
What are all substances made from?
Atoms
What is an atom?
The smallest part of an element that can exist
How many elements are there?
About 100
Where are elements shown?
Periodic table
How are compounds formed?
chemical reactions of elements
What is a chemical reaction?
The formation of 1 or more new substances - often involving a detectable energy change
What are compounds?
Contain two or more elements chemically combined in fixed proportions
How do you separate compounds into elements?
Chemical reactions
What is a mixture?
Two or more elements or compounds NOT chemically combined together
Why are mixtures different from compounds?
Chemical properties of each substance in the mixture are unchanged
What are the 5 ways that mixtures can be separated?
Filtration Crystallisation Simple Distillation Fractional distillation Chromatography
How do physical changes differ from chemical changes?
Do not involve chemical reactions
No new substances are made
What is the nucleus?
Middle of atom which contains protons and neutrons so has a positive charge
What are electrons?
Negatively charged particles that orbit the nucleus in shells
What is the mass of protons, neutrons and electrons?
Proton 1
Neutron 1
Electron 1/1830
What is the charge of protons, neutrons and electrons?
Proton +1
Neutron 0
Electron -1
What is the atomic number?
Number of protons/electrons
What is the mass number?
Number of protons + neutrons
What are isotopes?
Different forms of the same element which have the same number of protons but a different number of neutrons
What can new experimental evidence leads to?
Models being changed or replaced
Before the discovery of the electron, what were atoms thought to be?
Tiny spheres that couldn’t be divided
What did the discovery of the electron lead to?
The plum pudding model of the atom - suggesting that the atom was a ball of positive charge with negative electrons embedded in it
What did alpha particle scattering experiments lead to?
The conclusion that the mass of an atom was concentrated at the centre and was charged (nucleus) - this nuclear model replaced the plum pudding model
How did Neil’s Bohr adapt the nuclear model?
He suggested that electrons orbit the nucleus at specific distances - the theory agreed with experimental observations
What happened after Niels Bohr adapted the nuclear model?
Experiments led to the idea that positive charge of the nucleus can be subdivided into a number of smaller particles each with the same amount (protons)