ASTR-1010 Lecture Notes - Lecture 7: Mass Number, Atomic Mass, Atomic Number

• School: Vanderbilt University
• Department: Astronomy
• Course: ASTR-1010
• Professor: Stassun Keivan

Document Summary

Although it is the s(cid:373)allest part of the ato(cid:373), (cid:373)ost of the ato(cid:373)(cid:859)s (cid:373)ass is (cid:272)o(cid:374)tai(cid:374)ed i(cid:374) the (cid:374)u(cid:272)leus. The ele(cid:272)tro(cid:374)s do (cid:374)ot really (cid:862)or(cid:271)it(cid:863) the (cid:374)u(cid:272)leus; they (cid:862)s(cid:449)ar(cid:373)(cid:863) i(cid:374) a (cid:272)loud (cid:449)hi(cid:272)h gi(cid:448)es the ato(cid:373) its size. Atomic mass #= # protons + # neutrons. Atomic mass number = 2: **difference: added neutron in the nucleus. The number of protons and neutrons in the nucleus determine the element & isotope. **different isotopes of a given element contain the same number of protons but different # of neutrons. 4he : 4 = atomic mass number ( p + n); he is the element, which will tell us the number of protons. Ion (meaning the number of protons is not equal to the number of electrons) Molecule: two or more atoms combined to form a particle (water, carbon dioxide) The phases: solid, liquid, gas, plasma. Depend on how tightly bound the atoms and/or molecules are.