atoms, bonding & molecular polarity U.1 L.2

oxygen, carbon, hydrogen, nitrogen, phosphorus and sulfur make up 99% of all living organisms

isotopes are atoms of the same element that vary in the number of neutrons

since they all have the same number of electrons all isotopes of a element usually have the same chemical properties

electrons are important because they control the chemical behaviour of an element, atoms with incomplete valance shells are chemically reactive

elements will lose/gain electrons or share electrons to gain stability

intramolecular bonds are bonds formed by sharing or transferring electrons, (ie. ionic bonds, the transfer of electrons or covalent bonds, the sharing of electrons)

cations are positively charged ions and they lose electrons

anions are negatively charged ions and they gain electrons

octet rule : atoms tend to gain, loe, or share electrons so as to have 8 electrons

ionic bonds occur when one atom donates or gives up one or more electrons, for example, sodium donates an electron to chlorine making it a sodium ion and a chloride ion creating sodium chloride, positives and negatives attract to each other and form an ionic compound

polarity is the sharing of electrons, and a molecule with a larger atom will have a stronger pull, therefore it can outpull other electrons (which is what polarity is - the equal/unequal pull when sharing electrons)

polar covalent bond : when electrons are shared unequally, due to different elements having different electronegativities

non-polar covalent bonds are when electrons are shared equally

higher electronegativity = stronger pull of shared electrons

polar molecules have dipoles

a dipole is a charge due to unequal sharing of electrons

the molecule as a whole is neutral, but has parts that act like they are changed depending on how much time electrons are spending there

polarity allows molecules to blend in or to dissolve

role of solubility : like dissolves like

hydrophilic (water loving) compounds dissolve in water because they are polar/charged and can form intermolecular bonds (for example salt where dipoles of water attracted to charged ions, or sugar where dipoles from polar molecules attract to dipoles of water)

hydrophobic (water hating) compounds do not dissolve in water because they are non-polar and cannot bind to it

intermolecular bonds are bonds between different molecules

hydrogen bonds are weak forces between polar molecules and hydrogen of another molecule, due to dipoles, between hydrogens and molecules with N,O,F

water is polar, and therefore can attract other water molecules which is COHESION

it also attracts to other molecules (non-water) which is ADHESION

london bonds/forces are bonds between all molecules, they end to be weaker, and are a temporary unequal distribution of electrons (dispersion forces)

van der waals : a bond between dipole-dipole/polar molecules