CHEM Flashcards
LEARN DIS
What is an atom?
The smallest part of an element that can exist.
What is an element?
A substance made of only one type of atom.
Name the three subatomic particles?
Protons, Neutrons and Electrons
State the relative masses and charges of the subatomic particles.
Mass: Proton = 1, Neutron = 1, Electron = Negligible. Charge: Protons = +1, Neutron = 0, Electron = -1.
What is the plum pudding model?
a ball of positive charge with negative electrons embedded within it.
What did the gold foil experiment (alpha particle scattering) prove?
That atoms have a dense nucleus with a positive charge?
What did Chadwick discover?
The neutron
What did Bohr’s experiment show?
That electrons are in specific shells.
What is the atomic number in an atom?
The number of protons in an atom.
What is the mass number of an atom?
The number of protons + the number of neutrons
In the electron shell model how are the subatomic particles arranged in an atoms?
Protons and neutrons in the nucleus , electrons orbiting in shells.
Why is the number of electrons in an atom equal to the number of protons?
As their charges cancel out.
How many electrons can go in the first shell?
2
How many electrons can go in the second and third shells?
8
What are the groups in the periodic table?
The columns numbered 1, 2, 3, 4, 5, 6, 7, 0
What can the group tell you about the electrons in an atom?
How many electrons are in the outer shell.
What are periods in the periodic table?
The rows
What can the group tell you about the electrons in an atom?
How many shells an atom has
Why do atoms have no overall charge?
The number protons and neutrons are the equal.
What are isotopes?
Atoms of the same element with a different number of neutrons.
What is abundance?
The % of atoms in a sample with a particular mass.
What is the relative atomic mass of an element?
And average value for the mass that takes account of the abundance of the isotopes of the element.
What is relative formula mass?
The sum of relative masses of each atom in a compound.
What symbol do we use for relative formula mass?
Mr
In the modern periodic table how are the atoms arranged?
By their atomic number and in groups according to their chemical properties.
Why did Mendeleev leave gaps in his periodic table?
For elements that had not been discovered yet.
Why do elements in the same group have similar properties?
Because they have the same number of electrons in their outer shell.
Before the discovery of protons, neutrons and electrons, how did scientists organise the elements?
By atomic weight
Which discovery meant that their organising elements by atomic weight was not always correct?
Isotopes
Where are the metals on the periodic table always found?
To the left and the bottom of the periodic table.
What name is given to elements in group 0?
Noble gases
Why are the elements in group 0 so unreactive?
They have full outer shells so do not need to gain or lose electrons.
How does the boiling points of group 0 change down the group?
Increases down the group
Explain why the group 1 elements are called alkali metals?
They are metals that form alkalis when they react with water.
What are the products of the alkali metals in a reaction with with: oxygen, water and halogens?
Oxygen: Metal oxide.
Water: Metal hydroxide + hydrogen
Halogen: Metal Halide
Explain why group 1 elements get more reactive down the group?
More electrons, more shielding , weaker electrostatic from the nucleus to the outer shell, easier to lose and electron.
What name is given to elements in group 7?
Halogens
How does the boiling point change down the group?
Increases down the group c
Explain why group 7 elements get less reactive down the group?
More electrons, more shielding, weaker electrostatic, attraction from the nucleus to the outer shell, easier to lose and electron.
What is a displacement reaction?
\where a more reactive element displaces a less reactive one from a compound.
Where are the transition metals found in the periodic table?
In the middle
Compare the melting point, density, strength, hardness and reactivity of transition metals with group 1 metals.
Higher for all but reactivity.
What is distinctive about the ions formed by transition metals?
Can form ions with different charges
What is distinctive about compounds formed from transition metals?
They are coloured.
What can transition metals be used for?
Catalysts
How do you calculate Relative atomic mass?
(% abundance isotope 1 x mass isotope 1) + (% abundance isotope 2 x mass isotope 2) over 100
What is relative molecular mass and how so you calculate it?
Relative molecular mass is the mass of a molecule. NH3 becomes 14 + (1x3) = 17. Find the atomic mass of each element and if multiple times the atomic mass by that number.
What are the common physical properties of metals?
Solid and Shiny, Conduct electricity and heat, strong, malleable and ductile.
What are the common physical properties of non-metals?
Dull, Brittle, Not malleable or ductile, insulating.
