Topic 1 - Atomic Structure And The Periodic Table Flashcards
What does the atomic number tell you?
How many protons there are
What does the mass number tell you?
The total number of protons and neutrons in the atom
Definition of element
An element is a substance that consists of only one type of atom
Definition of ‘Isotope’
Different forms of the same element, which have the SAME number of PROTONS but a DIFFERENT number of NEUTRONS
Extra info on isotopes…
- Isotopes are the same as the element except for extra NEUTRONS
- Isotopes have the same atomic number but different mass numbers
Popular example of a pair of isotopes?
Carbon-12 and Carbon-13
Carbon-12
6 PROTONS
6 ELECTRONS
6 NEUTRONS
Carbon-13
6 PROTONS
6 ELECTRONS
7 NEUTRONS
What do we refer to when talking about the mass of element as a whole?
- Relative atomic mass (Ar) is used instead of mass number when referring to the element as a whole.
- Why? Because many elements exist as a number of different isotopes, takes it into account
Relative Atomic Mass definition
Relative atomic mass is an average mass taking into account the different masses and abundance’s (amounts) of all the isotopes that make up the element
Formula for RAM
RAM (Ar) = sum of (isotope abundance x isotope mass number)
———————————
Sum of abundances of all the isotopes
Compounds (brief)
- Atoms join together to make compounds
- When elements react, atoms combine with other atoms to form compounds
- Properties of a compound are usually totally different from properties of the original elements.
Compounds (in-depth)
- Compounds are substances formed from two or more elements
- The atoms of each are in fixed proportions throughout the compound
- atoms held together by chemical bonds
What making bonds involves:
- Making bonds involves atoms giving away, taking or sharing electrons
- Only electrons involved, nuclei of atoms aren’t affected at all when a bond is made
Can you separate original elements of a compound?
It’s usually difficult to separate original elements of a compound out again, chemical reaction needed to do so
Ionic bonding
- A compound formed from a metal and a non-metal consists of ions
- Metal atoms = lose electrons to form positive ions
- Non-metal atoms = gain electrons to form negative ions
- Opposite charge of ions mean that they’re strongly attracted to each other (called ionic bonding)
Examples of compounds which are bonded ionically:
- Sodium chloride
- Magnesium oxide
- Calcium oxide
NaCl Sodium Chloride, how is it bonded ionically
A sodium atom gives an electron to a chlorine atom.
Covalent bonding
- A compound formed from a non-metal consists of molecules
- Each atom shares an electron w/ another atom (called covalent bonding)
Hcl Hydrogen Chloride, how is it bonded covalently?
A hydrogen atom bonds w/ a chlorine atom by sharing an electron w/ it
Iron reacts with sulphur?
The compound formed is a dull grey solid lump, doesn’t behave anything like iron or sulphur.
Formula
- Represents a compound
- Made up of elemental symbols
- Shows what atoms are in a compound
Carbon Dioxide (CO2)
- A compound formed from a chemical reaction between carbon and oxygen
- Contains 1 carbon atom and 2 oxygen atoms
Sulphuric acid (H2SO4)
Each molecule contains: 2 hydrogen atoms, 1 sulphur atom and 4 oxygen atoms
Calcium Hydroxide Ca(OH)2
Contains 1 calcium atom, 2 oxygen atoms and 2 hydrogen atoms
What does a bracket in a formula mean (e.g. Ca(OH)2)?
Means that the little number outside applies to everything inside the brackets