Biochemistry: Atom and Covalent Bond-­‐ Atoms Essay

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Pages: 7

BIOCHEMISTRY NOTES

-­‐UNIT 2-­‐

ATOMS • • ________________-­‐ the basic unit of matter. Contains subatomic particles o _____________________ (+ charge) o _____________________ (no charge/neutral) o _____________________ (-­‐ charge) • • ELEMENTS AND ISOTOPES • • ___________________-­‐ a pure substance that consists of only one type of atom. Elements are represented by a 1 or 2 letter symbol. (ie: C = carbon) The number of ___________________ in an element is that element’s _______________________.

o The atomic number of carbon is 6, therefore carbon has 6 protons and consequently 6 neutrons. • ISOTOPES • _________________-­‐ atoms of the same element that have different numbers of neutrons. o Isotopes are identified by their _________________________________________________ (ie: carbon-­‐12, carbon-­‐13, carbon-­‐14) • • The _____________________________________________ of the masses of an element’s isotopes is called its _____________________________.

Isotopes have the same number of _______________________, so all isotopes of an element have the same ______________________________________. Mass Number-­‐ the sum of the number of ________________________ plus the number of ________________________. Protons and neutrons have about the same mass. Electrons are much ________________. Atoms have equal numbers of __________________________ and ___________________________. o Because these particles are opposite charges, the whole atom is _______________.

RADIOACTIVE ISOTOPES • Some isotopes are _____________________________. This means that their nuclei are unstable and break down at a continuous rate over time. IONS • _______________-­‐ an atom that has gained or lost an electron, giving it a positive or negative charge. o ___________________-­‐ a positively charged ion o ___________________-­‐ a negatively charged ion CHEMICAL COMPOUNDS • _______________________-­‐ formed by the chemical combination of two or more elements in definite proportions. o Compounds are typically written as a __________________________________________ (ie: NaCl, CO2, etc.) This gives you the ratio elements in the compound. o The physical and chemical properties of a compound are usually very different from those of the elements form which it is formed. • • CHEMICAL BONDS • ___________________________________-­‐ formed when one or more electrons are transferred from one atom to another.

o Form between a _____________________ and a…