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CHAPTER 6: Periodic Table. Development of Periodic Table. Mendeleev Contributions – made very first periodic table p.t. arrangement: elements ordered by increasing atomic mass. Development of Periodic Table. 3) Noticed periodic pattern (repetition) in element properties - PowerPoint PPT Presentation
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Development of Periodic Table
► Mendeleev1) Contributions – made very
first periodic table
2) p.t. arrangement: elements ordered by increasing atomic mass
3) Noticed periodic pattern (repetition) in element properties- elements placed in groups w/ similar properties
- Left gaps for substances yet to be discovered
Development of Periodic Table
4) errors: when new elements discovered, several elements on his table didn’t fit right- had different properties
Moseley
►periodic table arrangement: elements ordered by increasing atomic number
►Periodic Law – when elements arranged by increasing atomic number, their physical & chemical properties show a periodic pattern
Modern Periodic Table
► Boxes contain:1) Element name2) Element symbol3) Atomic number4) Atomic mass
Modern Periodic Table
►Arrangement – increasing atomic numbera) groups – columns (vertical)b) periods – rows (horizontal)
Classifying Elements
►Metals – elements w/ shine
– solid @ room temp– conducts heat & electricity– malleable: put into thin wires– ductile: pound into sheets
Metals
a) Alkali Metals – group 1A (except H)- highly reactive, very soft
b) Alkaline Earth Metals – group 2A- less reactive and denser
than alkali metalsc) Transition Metals – d-block (group
3-12B)
Metals
d) Inner transition metals – f-block
i) Lanthanide Series – row 1 of f-blockii) Actinide Series – row 2 of f-block
La
Ac
Nonmetals
►Defn - gases or brittle, dull looking solids
- poor conductors of heat & electricity
a) Halogens
b) Noble Gases
- group 17A
- highly reactive- group 18A
- very unreactive/stable
Metalloids
►Defn – BORDER THE STAIRSTEP LINE
- Have similar chem & phys props as both metalsand nonmetals
Alk
ali
meta
ls
Alk
alin
e e
art
h m
eta
ls
Transition Metals Halo
gens
Noble
Gase
s
LanthanidesActinides
Organizing Elements By Electron Configuration
►Valence Electron – electrons in highest energy level
atoms in same group have similar chemicalprops b/c they have same # of valence e-
Valence Electrons And Period
►The period indicates what energy level the valence electrons are located on
►Ex: [Ar] 4s2 3d10 4p13 Valence e-
on 4th energylevel
Valence Electrons and Group Number
►# of valence electrons equals group number (only for main group elements)
► exception: Helium(in group 18, but has 2 valence e- only)
Ex Problems
►Tell the group, period, and block where these elements are located
[Ne] 3s2
group –
period –
block –
[He] 2s2 2p4
group –
period –
block –
[Kr] 5s2 4d105p5
group –
period –
block –
2 1716
3 2 5
s p p
Periodic Trends
►There are certain patterns that occur with the elements as you go across and down the periodic table
which atom is the biggest? smallest?which atom is most reactive/least stable?
Atomic Radius (size)
►Defn – distance from center to edge of electron cloud
►Period Trend – decreases from left to rightWhy?
increasing # of protons (+ charge) in nucleus has a greater attraction for
electrons (- charge)
Atomic Radius►Group Trend – increases from top to
bottomWhy?
electrons occupy higher energy levels and are farther from the nucleus
Period 1 Period 2Period 3
Ion
►Defn – atom w/ a positive or negative charge- atom lost or gained electrons- # protons ≠ # electrons
Cation
►Defn – positive ion (atom lost e-)- more protons than electrons
►Comparing atom size vs. its cation size
A
atom A
A+
cation of atom A
cations are SMALLER than its original atom
Anion
►Defn – negative ion (atom gained e-)- more electrons than protons
►Comparing atom size vs. its anion size
A
atom A
A-
anion of atom A
anions are LARGER than its original atom
Ionization Energy
►Defn – energy required to remove an electron from an atom
►Period trend – IE increases from left to rightWhy?
increased nucleus charge has greater hold on valence e-
Ionization Energy
►Group Trend – IE decreases from top to bottom
Why?atomic size increases, valence e-
are farther away so easier to remove (less energy required)
Ex problem
►Rank these atoms from increasing to decreasing ionization energy: Ba, Cs, Cl
Cs Ba
Cl
increases
decr
ease
s
Cl > Ba > Cs
Electronegativity
►Defn – relative ability of an atom to attract electrons in a chemical bond “how badly does atom want electrons” while in a bond
►Period Trend – increases from left to right
►Group Trend – decreases from top to bottom