SJ # 5 2-1 “Inside an Atom” p. 50-54
*nucleus: the tiny central core of an atom
inside
the
nucleus
*protons (+):
*neutrons (o):
ex: Be
proton # = atomic #
neutron # = (atomic mass – atomic #)
Atomic mass = ??
Atomic # = ??
9-4 = 5 neutrons
*electrons: (-) move very rapidly around the nucleus,
# = proton # (but # of e- can change!) (7)
Mass & Volume of Atoms:
*protons (p+) and neutrons (n) are about 2000 times as massive as
electrons (e-)!!
*p+ and n give an atom its mass
*e- give an atom its size or volume (space it takes up) (2,3,4,5)
*Fig. 1 p. 51 drawing of an atom
--count p+, e-, and n
--what element is it?
*Draw an atom of lithium (Li)
*valence electrons: *e- that are the farthest away from the nucleus
*the most loosely held electrons
*determine MANY properties of the atom/element
*they are involved in bonding,
by either getting transferred or shared
*electron dot diagram: *also called Lewis structures
*a way to show how many val e- an atom has
*includes symbol of element and val e-
E
H
H
C
Al
*p. 52-53 Models of Atoms Timeline: as we read each capsule, determine what each
person got right and what they got wrong.
2-1 Review “Inside an Atom” p. 54 #1-5 (use your notes to answer)
1. Draw an atom of oxygen, labeling p+, n, and e-. Use the drawing of lithium in our notes as
a guide.)
2. Explain why the electrical charge on an atom is zero, or neutral.
3. What happens to val e- during the formation of chemical bonds?
4. Explain why e- make up most of an atom’s volume, but not much of its mass.
5. What info can you get from an e- dot drawing?