Unit 2 -atomic Structure
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Relative mass and charge of a proton
Charge = +1 Mass = 1
Relative mass and charge of neutrons
Charge = 0 or neutral Mass = 1
Relative mass and charge of electron
Charge = -1 Mass = 0.0005
What is the atomic number of an element?
The number of protons in the nucleus (this is what defines an element). Found at the bottom left of an element card
What is the mass number of an isotope/element
The total number of protons and neutrons in a nucleus. Found top left of an element card
What is an isotope
The different forms of the same element that contain the same number of protons but different number of neutrons in the nucleus. They differ in relative atomic mass but not in chemical properties
What is the relative atomic mass
The relative atomic mass of an element (Ar) is an average value of mass for the isotopes of the element compared to 1/12 of carbon (RAM 12)
How to work out relative atomic mass of an element from the relative abundances of its isotopes
Add the percentages of each isotope. Eg ISO1 = X mass, y% ISO2= A mass, B% RAM = (X * Y/100) + (A * B/100)
What does an atom consist of ?
Atoms consist of a central nucleus, composed of protons (+1) and neutrons (+/-0), surrounded by electrons (-1) in orbiting shells
How many electrons can each shell hold ?
Maximum of 2 X n² ie. Shell 1 = 2 e Shell 2 = 8 e Shell 3 = 18 e Shell 4 = 32 e
Number of electrons in a neutral atom =
Number of protons
What is a cation
A positively charged ion Has more protons than electrons Cations are PUSSitive
What is an anion
A negatively charged ion. Has more electrons than protons
How are ions formed
When a neutrally charged atom gains or loses electrons
What is ionic bonding
Bonding between a metal and a non metal. The metals lose electrons and give them to the non metals so that they can become stable (8 electrons in the outer shell). This bonding is strong electrostatic attraction between oppositely charged ions
What elements have stable electron arrangements (8 electrons in the outer shell)
Noble gasses
Can you predict the charge of an ion from ionic bonding?
Yes. See how many electrons it has in its outer shell and see how many it needs to gain/lose in order to have 8 electrons in its outer shell.
Do ionic compounds have high melting points?
Yes. Ionic compounds have high melting and boiling points because of the strong electrostatic attraction between oppositely charged ions.
What is an ionic crystal
An ionic crystal is a three-dimensional lattice structure held together by attraction between oppositely charged ions
What is electric currant
Electric current is the flow of electrons or ions
In what state will ionic compounds conduct electricity
Ionic compounds will only conduct electricity when molten or in a solution
Why do ionic compounds only conduct electricity when molten or in a solution
Because of the attraction between the anions and cations, the ions/electrons are not free to move in a solid state. However, when molten or dissolved, these ions are free to move
What is a covalent bond
The sharing of a pair of electrons between two atoms in order to become stable. Covalent bonding only happens in non-metals. Covalent bonding is a strong attraction between the bonding pair of electrons and the nuclei of the atoms involved in the bond
Do covalent compounds with simple molecular structures have high or low melting/boiling points
Covalent compounds have low melting/boiling points. Even thought the covalent bonds are very strong, the molecules are held together by weak forces. Therefore, covalent compounds how low melting/boiling points