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WHAT IS THE BODY? (Univ. of Aberdeen) (Molecules (Atoms versus ions…
WHAT IS THE BODY? (Univ. of Aberdeen)
Molecules
The periodic table
Elements
Chemical element abbreviation
Ordered according atomic number (protons)
Grouped according to their properties
Atomic weight / Atomic mass
Nº of protons and neutrons
Protons
Positive charge
Subatomic particles
Neutrons
Subatomic particles
No charge
Two categories
Metals
Alkali metal
Alkaline earth metal
Lanthanide
Actinide
Transition metal
Post-trasition metal
Non-metals
Polyatomic non-metal
Diatomic nonmetal
Noble gas
Metalloid
Metal properties
Non-metal properties
Electrons
Subatomic particles
Negative charge
Found in the outer 'shells' of an atom
Each shell holds a certain number of electrons
General formula: 2(n²)
Atoms versus ions
Atoms
Elements in their neutral form
Charges
Come from proton (+1)
Come from electon (-1)
Neutral form
The charges cancel each out
Overall is zero
Ions
Do have a charge
Imbalance between protons and electrons
Happen naturally
If electrons are lost
Biochemical reactions
Definition
Formed when atoms from one or more elements are joined together.
Atoms joined by ionic bounds
Ionic compounds / Molecules (less common)
Atoms joined by any type of bond
Compounds
Molecules made up of multiple elements
Vary in size and complexity
Biomolecules
Considering biological matter
Examples
Single elements
Helium (He)
Oxygen (O2)
Ozone (O3)
Multiple element molecules
Water (H2O)
Bonds
Ionic bonds
Formed when atoms gain or lose electrons
Charges
Like charges repel one another
Opposite charges repel one another
Ions of opposite charges
Attract one another
Bonds the atoms together
Ionic bonding
Examples
Sodium chloride (NaCl)
Sodium atom (Na)
Loses an electron
Resulting in a positively charged sodium ion (Na+)
Chloride atom (Cl)
Gains an electron
Making it a negatively charged chloride ion (Cl-)
The Na+ and Cl- are attracted to each other
Join together to form NaCl
No charge
The (+) and (-) charges cancel each other
Covalent bonds
Formed by the sharing of electron pairs
Shells
Each shell has a max. num. of electons
The max. num. of elect. changes with each shell
Elect. like to be in pairs
Atoms are always aiming to have a full complement of elec. in the out shell, or have it empty altogether
1 atom has 12 electrons
1 pair in its first shell (max. 2)
4 pairs in its second shell (max. 8)
1 pair in the outer shell (max. 18)
Aim to find another 8 pairs of electrons
Or to get rid of the one pair to empty this shell
Definition
The sharing of electrons and electron pairs between atoms
To help them get their full complement of electrons in the outer shell
Eletrostatic forces
Attraction between the (+) nucleus and the negatively charged and shared electrons.
Electronegativity
The measure of the strength of the force on the electrons
Examples
Water
Oxygen
6 electrons in its 2nd shell
So is missing 2 to get its full complement
Hydrogen atoms
1 electron in their outer shell
So want 1 more.
By combining 1 O with 2 H
Each atom can then have a full complement of electrons in its outer shell