Atomic Structure And The Periodic Table Flashcards
What’s an atom
An atom is the smallest part of an element that can exist. All substances are made of atoms.
How many elements are there?
There are about 100 different elements.
What are compounds formed from?
Compounds have from 2 or more different elements chemically combined in a fixed proportion
What can a compound be separated into?
Compounds can only be separated into elements by chemical reactions
What is a mixture?
A mixture consists of two or more elements or compounds, not chemically bonded together
What’s the charge of an electron?
-1
What’s the relative mass of a neutron?
1
What’s the relative mass of an electron?
Very small or 0
What’s the charge of a neutron?
Neutral or 0
What’s the relative mass of a proton?
1
What does the ‘mass number’ of an atom equal to?
protons + neutrons
What does the ‘atomic number’ of an atom tell you?
The number of protons in an atom has
What’s the charge of a proton?
1
How can you work out how many neutrons an atom has
Number of neutrons = mass number - atomic number
How can mixture be separated by physical processes?
These are physical processes that do not involve chemical reactions and no new substances are made.
- Filtration
- Crystallization
- Simple distillation
- fractional distillation
- Chromatography
Describe and explain filtration? Give examples.
It is used to separate and insoluble solid from a liquid.
Eg. Are useful for separating a mixture of sand and water, or access reactant from a solution. Filtration works because the filter paper has tiny holes or pores in it.
Describe and explain crystallization. Give examples.
A process which helps to separate a pure solid from a solution and it’s crystal form
Eg. The salt we get from seawater can have many impurities in it.
Describe and explain simple distillation. Give some examples.
It is used to separate a solvent from a solution. When the solution is heated the solvent vapor evaporates from the solution. Ex. Pure water from sea water
Describe and explain Fractional distillation. Give examples.
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
Describe and explain chromatography. Give examples.
used to separate mixtures of soluble substances (separating components of a mixture.) ex. coloured substances such as food colourings, inks, dyes
Before the discovery of electrons, what were atoms thought to be?
Atoms were thought to be tiny spears that could not be divided
What did the discovery of the electron lead to?
It led to the plum pudding, model of the atom
What was the plum pudding Model suggested to be
It was suggested that the atom is a ball of positive charge with negative electrons embedded in it
What was replaced instead of the plum pudding model
The nuclear model
What did the alpha practical lead to?
It led to the conclusion that the mass of an atom was concentrated at the center (nucleus) and that the nucleus was charged.
What’s the difference between the plum pudding model of the atom and the nuclear model of the atom?
In the plum pudding model has a positive sphere with negative charge randomly placed within the sphere and there is no empty space.
In the nuclear model there is a central positive tiny nucleus with mostly empty space and lots of negative charges .
Why did the new evidence from the scattering experiment lead to a change in the atomic model?
Because the mass of an atom is concentrated at the center (nucleus) and that the nucleus was charged. This lead to the plum pudding model being replaced by the Nuclear model.
In an atom what are the number of electrons equal to?
The number of protons in the nucleus
Do atoms have an electric charge
No. Atoms have no overall electric charge.
What are the number of protons in an atom of an element equal to?
It is the atomic number
Do all atoms of a particular element, have the same number of protons. Yes or no?
Yes
Atoms are very small. What is the radius of an atom
The atoms radius is about 0.1 nm (1 x 10^-10m)
Where are almost all of the masses of an atom in?
The nucleus
Atoms of the same element can have different numbers of neutrons. What are these atoms called?
isotopes of that element
What are isotopes?
Isotopes are different forms of the same element, which have the same number of protons, but a different number of neutrons (same number of protons but different mass numbers)
What is the formula of the relative atomic mass?
Relative atomic mass(Ar) = sum of (isotope abundance x isotope mass number) / sum of abundance of all the isotopes
What is an element?
An element is a substance made up of only one type of atom.
Describe atoms using the nuclear model
Atoms are consists of a tiny central nucleus that is dense and positively charged the nucleus is surrounded by negatively charged electrons most of the atom is empty space.
The radius of a nucleus is less than the atom. What’s the radius of a nucleus?
1×10^ -14
How did scientists attempt to classify the elements before the discovery of protons, neutrons and electrons
Scientists would arrange them in order of their atomic weights 
Elements that react to form positive ions are what
Metals
Elements that do not form a positive ion are what
Non-metals
How many electrons in the outer shell do noble gases have
8, except for HELIUM which has only 2 electrons
The boiling point noble gases increase What else increases?
The relative atomic mass (Going down the group)
What are elements in group one of the periodic table known as
Alkali metals that have there characteristic properties because of the single electron in the outer shell
In group one is the reactivity of the elements increase. going down or up the group?
Down
What are the elements in group 7 known as
Halogens
What is similar between all halogens
They all have similar reactions because they all have seven electrons in the outer shell
Halogens are non-metals what do they consist of
molecules made of pairs of atoms
Further down group 7 it has a higher…
Relative molecular mass, melting point and boiling point
What happens to the reactivity in group 7
The reactivity of the elements decrease going down the group
In the early periodic table how were the elements set up
The elements were set by the atomic weight
Explain the difference between nonmetals and metals
Metals are good conductors of electricity
Good conductors of heat
have a high density and are Shiny
Nonmetals are dull
Have a low melting point
Poor conductors of electricity
Low density
Explain simple distillation
Simple distillation is used to separate a liquid from a solid if we want to keep the liquid
Explain fractional destalasation
Fractional destination allows us to separate two different liquids
More reactive halogens can be displaced by a
Less reactive halogen from an aqueous solution of its salt
What was Niels Bohrs theory
He adapted the nuclear model by suggesting electrons orbit the nucleus at a specific distance
After Niels Bohr experiment led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles what were the name of these particles?
Protons
What did James Chadwick Find out
That the nucleus contains neutrons
The early periodic table was restricted to the order of the atomic weight then Mendeleev overcame some problems what did he do
Mendeleev left gaps of elements he thought had not been discovered then they became discovered and the knowledge of isotopes made it possible to explain why the order based on atomic weight was not always correct
