Atomic theory 1 Flashcards
Define Element
A substance that cannot be broken down into simpler substances by chemical means.
How are elements arranged horizontally?
In periods
How are elements arranged vertically?
In groups
What does the number of electrons in the outer shell give rise to and what does it mean?
Valency - which means the number of chemical bonds an element can make.
What is the name of group 1
Alkali metals (1 electron in outer shell, valency =1)
What is the name of group 2
Alkaline earth metals (2 electrons in outer shell, valency = 2)
What is the name of group 7
Halogens( 7 electrons in outer shell, valency = 1)
What is the name of group 0?
Noble gases ( 8 electrons in outer shell, valency = 0\0
Protons
Positively charged
Neutrons
Neutral
Electrons
Negatively charged
Where are protons and neutrons found?
In the nucleus of the atom
Where are electrons in orbitals (sub-levels) found?
Around the nucleus
Do ions have a charge?
Yes
Do atoms and molecules have a charge?
No they are neutral
Are the words atoms and ions interchangeable?
No as atoms and ions are completely different
What is the whole number above the symbol for the element called?
The atomic number (Z)
What is the decimal number below each element called?
The relative atomic mass number (Ar)
What does the atomic number tell us?
The number of protons an atom of the element will have.
What does the relative atomic mass give?
An average mass of all known isotopes of that element.
Define metal
Any element that loses electrons to form a positive ion (cation).
Define atomic number
The number of protons present in the nucleus of an atom.
Define mass number
The mass number is the number of protons plus neutrons in the nucleus of an atom.
Define isotopes
Isotopes are atoms of the same element that have the same atomic number but different mass numbers due to the different numbers of neutrons present in the nucleus.
Define relative atomic mass number
The average mass of an atom of an element compared to 1/12 the mass of the carbon - 12 isotope, taking relative abundances of the naturally occurring isotopes into account.
What is valency linked to?
‘Octet rule’
Valency of group 1
1
Valency of group 2
2
Valency of group 3
3
Valency of group 4
4
Valency of group 5
3
Valency of group 6
2
Valency of group 7
1
Valency of group 8
0
Alkali metals
- Extremely reactive
- Soft metals
- Low densities
- Shiny when freshly cut but tarnish rapidly due to reaction with air
Alkali metal + oxygen gas –>
Metal oxide
Alkali metal + water –>
Metal hydroxide + hydrogen gas
Alkaline earth metals
- Very reactive but less reactive than the alkali metals
- Magnesium reacts slowly with water
Halogens
- Very reactive non-metals
- Low melting and boiling points
Noble gases 3
- Gaseous at r.t
- B.P increases down group
- Least reactive of all elements (as have 8 electrons in outer shell - except He which has 2 electrons in its only shell)
What can particles be?
Atoms, molecules or ions.
Where is the mass of an atom concentrated?
In a small central nucleus consisting of protons and neutrons.
What is around the nucleus?
Electrons
Why can the mass of an electron often be ignored?
As its so small
In an atom what does the number of electrons always equal to?
The number of protons in the nucleus