GCSE Topic 1a - Atomic structure and history of the periodic table Flashcards
Columns of the periodic table are called…
Groups
Rows of the periodic table are called…
Periods
Name for group 1 elements
Alkali metals
Name for group 2 elements
Alkaline earth metals
Name for group 6 elements
Chalcogens
Name for group 7 elements
Halogens
Name for group 8 elements
Noble gases
The group number of an element provides what information about an atom in terms of electronic structure?
Number of electrons in the outer shell
The period number of an element provides what information about an atom in terms of electronic structure?
The number of electron shells
All elements same the group have similar chemical reactivity. Explain why.
They have the same number of electrons in the outer shell.
Explain why an atom is neutral
The number of protons and electrons are equal
Define an ion
An atom that has lost or gained electrons
Define a cation
A positively charged ion
Define an anion
A negatively charged ion
Relative mass and charge of a neutron
Mass: 1
Charge: 0
Relative mass and charge of a proton
Mass: 1
Charge: 1+
Relative mass and charge of an electron
Mass: 1/1850 OR 1/2000
Charge: 1-
Define an isotope
Different atoms of an element with the same number of protons and different number of neutrons.
OR
Different atoms of an element with the same atomic number and different mass number.
Define the term ‘relative atomic mass’
The weighted mean mass of atoms of an element compared to 1/12th the mass of an atom of carbon-12.
Explain why isotopes of an element have identical chemcial properties
They all have the same number of electrons in the outer shell
Explain why there are no bromine atoms with a mass of 80, but the atomic mass is 80
- The atomic mass is an average of different isotopes
- 50% of bromine atoms have a mass of 79
- 50% of bromine atoms have a mass of 81
Explain why the atomic mass of chlorine is 35.5 but there are no atoms with this mass
- The atomic mass is an average of different isotopes
- 75% of chlorine atoms have a mass of 35
- 25% of chlorine atoms have a mass of 37
Formula for calculating the relative atomic mass of chlorine
- (25/100 x 37) + (75/100 x 35) = 35.5
- 35 and 37 are the masses of the two isotopes of chlorine.
- 25/100 is 25% and is the percentage of the chlorine-37 isotope
- 75/100 is 75% and is the percentage of the chlorine-35 isotope
Formula for calculating the relative atomic mass of bromine
- (50/100 x 79) + (50/100 x 81) = 80
- 79 and 81 are the masses of the two isotopes of chlorine.
- 50/100 is 50% and is the percentage of the bromine-79 isotope
- 50/100 is 50% and is the percentage of the bromine-81 isotope
Electronic conguration of a lithium atom
2 , 1
Electronic conguration of a lithium 1+ ion
2
Electronic conguration of a fluorine atom
2 , 7
Electronic conguration of a fluorine 1- ion
2 , 8
Which element in period 2 has an atom with the electronic configuration 2,8?
Neon
Which element in period 2 has an ion with an electronic configuration of 2,8 and a charge of 1-?
Fluorine
The ion is F-
Which element in period 2 has an ion with an electronic configuration of 2,8 and a charge of 2-?
Oxygen
The ion is O2-
How many protons are there in the nucleus of a lithium atom?
Three
How many neutrons are there in the nucleus of a lithium atom?
Four
How many electrons are there in a lithium atom?
Three
How many electrons are there in the first shell of a lithium atom?
Two
How many electrons are there in the outer shell of a lithium atom?
One
How many electrons are there in the outer shell of a lithium ion?
Zero
Russian scientist who designed the modern periodic table
Dmitri Mendeleev
Note that the periodic table was not discovered. The elements were discovered.
Number of elements known to Dmitri Mendeleev
63
English polymath who designed a precursor to the modern periodic table
John Newlands
Law of Octaves
- The principle behind the arrangement of elements in John Newlands periodic table
- There were no gaps
- Every eighth element has the same properties as the first element.
Structure of Dmitri Mendeleev’s periodic table
- Most elements were arranged in order of increasing atomic mass.
- Each group of elements had similar chemical properties and a trend in physical properties.
- Gaps were left for new elements to be discovered.
- Some elements were not put in order of atomic mass, such as tellurium and iodine. This is because iodine has similar chemical properties to bromine in group 7, but tellurium does not.
Comparison of Mendeleev’s periodic table and the modern periodic table
- For the modern periodic table elements are arranged in order of increasing atomic number.
- Mendeleev could not put elements in order of increasing atomic number as protons were not discovered until later.
- Mendeleev left gaps for new elements to be discovered.
- The elements in the modern periodic table fit into the gaps that Mendeleev left and have chemical and physical properties similar to what he predicted.
- Mendeleev’s periodic table did not include the noble gases as these were not yet discovered.
- Mendeleev’s periodic table did not have a section for the transition metals.
