Atoms And Elements Worksheet Page 3
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18Practice 2-1
Write the name and the symbol of the element that fits each of the following
description.
a) the alkaline earth metal in the sixth period.
b) the metalloid in the third period.
c) the nonmetal in group IVA..
d) the halogen that is liquid at room temperature.
e) the group-VIIIB transition metal with properties similar to Ru.
f) the third-period element that exists as diatomic molecule.
Answer
a) Barium, Ba
b) Silicon, Si
c) Carbon, C
d) Bromine, Br
e) Iron, Fe
f) Chlorine, Cl
2.3 Composition of the Atom
Atom: The smallest unit of an element that retains the properties of that element.
Atoms are composed of three subatomic particles: protons, neutrons, and electrons.
Protons and neutrons are located in the center of the atom and form a compact core
termed the nucleus. The electrons are located in the considerably larger space outside the
nucleus.
Table 2.1 Properties and Location of Subatomic Particles
Subatomic
Charge
Mass
Mass
Location
Particle
(g)
(amu)*
-24
Proton
+1
1.67 x 10
1.01
nucleus
-24
Neutron
0
1.67 x 10
1.01
nucleus
-28
Electron
-1
9.11 x 10
0.000548
outside nucleus
* Atomic mass unit (abbreviated amu) is convenient for representing the mass of very
small particles.
-24
1 amu = 1.67 x 10
g
2-3
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