Transcript Properties of Elements - Red Hook Central School District

Properties of Elements
Atomic Radius
A measure of the size on an atom.
What determines an atom’s size?
Remember, the nucleus is very very small
and compact. It is the electrons that
determine how big the atom is.
Atomic Radius
It is hard to measure where the moving eare at any moment, so they can not be
easily used to measure size.
DEFINITION: Half the distance between the
nuclei of two adjacent atoms in a crystal
½ distance
Ionization Energy
DEFINITION: The amount of energy it takes
to remove the outermost e- from a neutral
atom in the gas phase
X + Ionization energy
Neutral atom
X+
Cation
+
eelectron
Electronegativity
DEFINITION: A measure of the attraction an
atom has for electrons when it is bonded
to another atom.
Scale is from 0.7 (low, Cs) to 4.0 (high, F)
Trends in Atomic Radius
Across a period: radius decreases because
there are more protons in each successive
atom’s nucleus, pulling harder on the eand making the atom smaller
Down a group: radius increases because
the atoms have more energy levels farther
from the nucleus, making the atom bigger
Trends in Ionization Energy
Across a period: I.E. increases because there are
more protons in each successive atom’s
nucleus, pulling harder on the e- and making it
harder to remove the eDown a group: I.E. decreases because the
atoms have more energy levels farther from the
nucleus, so the outer e- are less attracted to the
nucleus and are therefore easier to remove.
Also, inner e- “shield” the outer e- from the pull
of the nucleus.
Trends in Electronegativity
Across a period: Electronegativity increases
because there are more protons in each
successive atom’s nucleus, pulling harder on the
eDown a group: Electronegativity decreases
because the atoms have more energy levels
farther from the nucleus, so the nucleus has less
positive pull on the e-. Also, inner e- “shield” the
outer e- from the pull of the nucleus
Ionic Radius
If an atom GAINS e-, it gets bigger in size
So….negative ions (anions) are bigger
than their neutral atom
Ionic Radius
If an atom LOSES e-, it gets smaller in size
So… positive ions (cations) are smaller than
their neutral atom
Group 1 alkali metals
• Electron configuration ends with S1
• Lose this outermost e- easily (low
Ionization energy and electronegativity)
forming +1 cations
• VERY reactive! Francium is MOST
reactive
• Not found uncombined in nature
• Form stable compounds with non metals
like NaCl
Group 2 alkaline earth metals
• Electron configuration ends with S2
• Lose these 2 outermost e- easily (low Ionization
energy and electronegativity) but not as easily
as Group 1 metals losing only 1 e• Form +2 cations
• Reactive! (but not as much as Group 1)
• Not found uncombined in nature
• Form stable compounds with non metals like
MgCl2
Groups 3-12 transition metals
• Highest energy level ends with S2
but d-orbitals are being filled
• Tend to lose the S2 e- easily, forming +2 cations, but
many can also form +1 or +3 (multiple oxidation states)
• Less reactive than Groups 1 or 2
• Form colorful ions and compounds
Groups 13
• Electron configuration ends with S2P1
• Lose the three S2P1 e-, forming +3 cations
• Both metalloids and metals in this group
Groups 14
• Electron configuration ends with S2P2
• Don’t tend to form ions
• Non metals, metalloids and metals in this
group
Groups 15
• Electron configuration ends with S2P3
• Tend to gain 3 e-, forming -3 anions
• Non metals, metalloids and metals in this
group
Groups 16
• Electron configuration ends with S2P4
• Tend to gain 3 e-, forming -2 anions
• Non metals, and metalloids in this group
• Reactive! Tend to form stable compounds
with metals like MgO
Groups 17 Halogens
• Electron configuration ends with S2P5
• Tend to gain one e-, forming -1 anions. Very high
electronegativity and ionization energy. (F is highest
electronegativity with 4.0)
• Non metals only in this group
• Only group to have all three phases of matter at room
temperature (s, l, g)
• VERY Reactive! Not found uncombined in nature. Tend
to form stable compounds with metals like NaCl. Most
reactive is F.
Groups 18 Noble gases
• Electron configuration ends with S2P6
• Energy level is full
• Do not lose or gain e-. Do not form ions.
• UNreactive! Not found combined with
other elements in nature. Do not form
compounds.