m etal nonmetal metalloid malleable ductile atomic radius electronegativity ionization energy shielding Wolfram Viza Arlington 2010 Trend What is a trend a pattern or direction ID: 758360
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Slide1
Periodic Trends
Vocabulary:metalnonmetalmetalloidmalleableductileatomic radiuselectronegativityionization energyshielding
“Wolfram”,
Viza
Arlington, 2010Slide2
Trend
What is a trend?a pattern or direction
Starbucks Stock HistorySlide3
Periodic trends
The elements have trends, too. For example:Look at the zig-zag line on your periodic table. Metals are on the left, nonmetals on the right, and the metalloids are adjacent to the line.
Metals
Nonmetals
MetaloidsSlide4
Important side-note
Metalsshinygood conductors of electricity and heathardmalleableductilegive away electronsNonmetalsdullgood insulatorsbrittle
accept electrons
Metalloids
some properties of metals and some of nonmetalsSlide5
Important side-note
MetalsNonmetals
sulfur
bromine
carbonSlide6
Important side-note
MetalNonmetalSlide7
Periodic Trends
We’re going to look at trends on the periodic table for physical properties of elements. These are:atomic radiuselectronegativityionization energySlide8
Atomic Radius
Distance from the nucleus of an atom to the outermost electrons.Typically measured as half the distance between the nuclei of identical bonded atoms.The range is about 25 pm for the smallest atoms to about 250 pm for the largest atomsSlide9
Electronegativity
The ability of an atom in a chemical compound to attract valence electrons. The scale is from 0-4 with 0 meaning no attraction for valence electrons and 4 as the highest attraction.Slide10
Electronegativity
What do you think would affect the ability of an atom to attract electrons?Number of protons in the nucleus and distance of electron from nucleusWhen an atom gains or loses an electron, the atom is called an ion.
This is a negative ion because it gained an extra negative electron.Slide11
Ionization Energy
The energy required to remove one electron from a neutral atom of an element.What do you think would affect the amount of energy required to remove an electron?Number of protonsDistance from nucleus
This is a positive ion because it lost an electron.Slide12
Periodic Trends
You will now look at trends on the periodic table for atomic radius, electronegativity, or ionization energy.To do this, you will pick one of the following options and use Open Office to make two graphs:Option 1Atomic Radius values of group 1.Atomic Radius values of period 4.Option 2Electronegativity values of group 1.Electronegativity values of period 4.Option 3Ionization energy values of group 1.
Ionization energy values of period 4.Slide13
Questions
What trend do you see on each graph as you move across a period?What trend do you see on each graph as you move down a family?Slide14
Atomic Radius Trends
Decreasing Atomic Radius Increasing Atomic Radius Slide15
Electronegativity Trends
Increasing ElectronegativityDecreasing ElectronegativitySlide16
Ionization Energy Trends
Increasing Ionization EnergyDecreasing Ionization EnergySlide17
Why?
Why do these trends exist? Let’s take a look first at the elements in group 1 to find out about the trends in families.Slide18
Group 1
Shielding
: the blocking of the nuclear charge to the valence electrons by the core electrons. More energy levels = more shielding. (Valence electrons are circled.)
Two consequences of more shielding:
1) Less attraction to outer electrons by nucleus (lower electronegativity);
2) Easier to remove electrons from valence shell (lower ionization energy).Slide19
Why?
Now let’s look at some of the atoms in period 4.Slide20
Period 4
The number of protons increases as you go across a period, yet the shielding does not increase. More protons = more attraction of the electrons to the nucleus.
More attraction of electrons to nucleus = higher electronegativity, higher ionization energy, and smaller atomic radius.
K Ca Sc Ti V Cr