2.1.1 and 2.1.2- atomic structure and isotopes, compounds, formula and equations.
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What was stated in Dalton’s atomic theory? (4 marks)
• Atoms are tiny particles made of elements • atoms cannot be divided • All the atoms in an element are the same • atoms of one element are different to those of other elements
What did Thomson discover about electrons? (3 marks)
• They have a negative charge • They can be deflected by magnet and electric field • They have a very small mass
Explain the plum pudding model.
Atoms are made up of negative electrons moving around in a sea of positive charge.
what was Rutherford’s proposal after the gold leaf experiment? (4 marks)
• Most of the mass and positive charge of the atom are in the nucleus • Electrons orbit the nucleus • Most of the atom’s volume is the space between the nucleus and the electrons • Overall positive and negative charges must balance
Explain the current model of the atom
• Protons and neutrons are found in the nucleus • Electrons orbit in shells • Nucleus is tiny compared to the total volume of the atom • Most of atom’s mass is in the nucleus • Most of the atom is empty space between the nucleus and the electrons
What is the charge of a proton?
1+
What is the charge of an electron?
1-
Which particle has the same mass as a proton?
Neutron
Which two particles make a most of an atom‘s mass?
Protons and neutrons
Which letter is used to represent the atomic number of an atom?
Z
What does the atomic number tell about an element?
`Atomic number = The number of protons in an atom of that element
Which letter represents the mass number?
A
How is mass number calculated?
Number of protons + number of neutrons
How to calculate the number of neutrons?
Mass number - atomic number
Define isotope
Atoms of the same element with a different number of neutrons
Why do different isotopes of the same element react in the same way? (2 marks)
• Neutrons have no impact on the chemical reactivity • Reactions involve electrons, isotopes have the same number of electrons in the same arrangement
What are ions?
Charged particles that are formed when an atom loses or gains electrons.
What is the charge of an ion when electrons are gained?
Negative
What is the unit used to measure atomic masses called?
Unified atomic mass unit, u
Define relative atomic mass
The weighted mean mass of an atom of an element compared with one 12th of the mass of an atom of carbon-12.
What is the unit of relative atomic mass?
No units
Define relative isotopic mass
The mass of an atom of an isotope compared with one 12th of the mass of an atom of carbon-12
The relative isotopic mass is the same as which number?
Mass number
What two assumptions are made when calculating mass number?
• Contribution of the electron is ignored • mass of proton and neutron is taken as 1.0 u