Unit 2.2 -2.3: atom structure + isotopes Flashcards
State properties of proton
- Referred to as proton or atomic number
- Sub atomic particle
- Determines which element an atom is
- Relative mass of 1
- Charge of +1
Properties of neutrons
- Relative mass of 1
- No charge
- Atoms of the same element can have different numbers of neutrons
Properties of electrons
- relative mass of 1/2000
- charge of -1
- orbit nucleus because they are attracted to positive charge of protons in nucleus
- number of electrons = number of protons
What is the atomic number?
- known as proton number
- above symbol of element (smaller number)
- tells how many protons an atom has
What do groups and periods determine?
Periods/rows - how many electron shells an element has
Group - how many electrons an atom has in its valence shell
What is the nucleon number?
- known as mass number
- represent number of protons + number of neutrons in nucleus of atom
Describe the organisation of electrons in atoms
First shell - closed to nucleus, holds max 2 electrons
Second shell - holds max 8 electrons
Valence (outermost) shell - 8 electrons
The closer the shell to the nucleus, the lower the energy of the electrons in the shell.
Electrons always occupy the shell with the lowest possible energy.
What are noble gases?
Elements in the 8th group with full valence shells.
Very stable, not chemically reactive
What does having a full valence shell achieve?
It will make an atom very stable.
Atoms always try to get full valence shell, and will undergo bonding in order to achieve stability.
What is an ion?
An electrically charged atom formed when an atom loses/gains electrons to achieve a full valence shell
How are ions named?
Metal ions have the same name as metal ions
Non-metal ions change their endings to -ide. E.g. oxygen – oxide.
How do metallic versus non metallic elements get a full valence shell?
Metallic (groups 1-3): lose electrons from valence shell to become cations (positive ions)
Non-metallic (groups 5-7): gain electrons to fill their valence shell with 8 electrons and become anions (negative ions)
How do you draw a diagram for an ion?
- Write number of protons +p (e.g. 11p) and circle it
- Draw the valence shell with 2 or most often 8 electrons (dots or crosses)
- Draw square brackets around iron
- Write charge (e.g. 2+ not +2!!) on right upper corner of brackets
- Label ion with symbol + electrical configuration
(may need to draw original atom before hand and show one electron leaving/arriving)
What are isotopes?
A variation of an atom; atoms of the same element/that have the same proton number but have different number of neutrons, so a different nucleon number.
Have the same electronic configuration, so the same chemical properties.
What does it mean when an isotope in radioactive?
The nucleus of the atom is unstable, and can break up/lose sub-atomic particles.
How are isotopes represented?
With a nuclear notation:
- mass number is placed at the upper left of chemical symbol
- atomic number is placed at lower left of chemical symbol
