Human Anatomy and Physiology: USC Bridge 1.3 chemical bonds Flashcards
Chemical bonds
When atoms combine with other atoms they are held together by chemical bonds.
Electron shells
Electrons form the electron cloud stouthearted nucleus of an atom occupy regions of space
hold a specific number of electrons
closer to the nucleus the energy level is stronger than the electron shells further from the nucleus
Octet rule
Except for the first shell which is full with two electrons, atoms interact in a manner to have eight electrons in their outermost energy level or valence shell.
Chemically inert elements
Unreactive and stable elements because the outermost energy level/ valence shell is completely filled with electrons
noble gases: i.e. Helium or neon
Chemically reactive elements
Outermost energy level is not fully occupied by electrons
tend to gain, lose, or share electrons with other atoms to achieve stability- ionic, covalent, and hydrogen bond formation
Ionic bonds
A chemical bond between atoms formed by the transfer of one or more electrons from one atom to another
because opposite charges attract these ions tend to stay close together forming an ionic bond
Electron acceptor
Acquires a net negative charge and is called a anion
Electron donor
Acquires a net positive charge and is called a cation
Covalent bond
Electrons are shared so each atom is able to fill its outer electron shell at least part of the time.
Can be single, double or triple covalent bond.
Polar covalent bond
Unequal sharing of electrons. Slight negative charge at one end and a slight positive charge at the other end.
Non polar covalent bond
Equal sharing of electrons. Charge balanced among atoms
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Electronegativity
Small atoms with six or seven valence shell electrons attract electrons very strongly
electron hungry
O, N, and Cl
Electropositive
Atoms with only one or two valence shell electrons
their electron attracting ability is low so they lose their valance shell electrons
K and Na
Dipole
Two poles of charge also known as a polar molecule
Hydrogen bonds
More like attractions than true bonds
form when hydrogen atoms are attracted by electronegative atoms and a bridge is formed between them
common between dipoles such as water
responsible for water molecules to cling together forming surface tension
Most important determinant of an atoms bonding behavior is:
The number of valence shell electrons
When atoms gain electrons the become ________
charged
negatively
Covalent bonds occur when:
Electrons are shared between atoms
Water is a polar molecule. Oxygen is electronegative and hydrogen is electropositve. This means that oxygen pulls electrons away from hydrogen and becomes more:_________
Negative