[ppt]periodic trends powerpoint - atomic size &...
TRANSCRIPT
Dmitri Mendeleev
• 1834-1907; sequenced known elements in order of increasing atomic mass
• Elements with similar properties in same column.
• Called Periodic Table because it highlighted the repeated (periodic) patterns of properties.
Periodic Law
• Chemical & physical properties of the elements repeat in a regular, periodic pattern when arranged by atomic number
• This is the basis for the modern periodic table – arranged by atomic number.
The Modern Periodic Table
• Using the information in your data booklet, complete the periodic table worksheet.
• Be sure to include a legend on your worksheet.
Alkali metals (not H) Alkaline earth metals
Transition metals Halogens Noble gases Inner transition Inner transition
G GGG
GG
G GGG
GG
L
L
VIIAVIAVAIVAIIIAIIAVIIAIA
Metalloids
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• Group Names:– Two systems: Old & New
• Old: Roman numerals with either A or B• New: Integers 1-18 from left to right• Group VA = Group 15
• Alkali Metals: – Group 1– Soft, light, reactive metals
• Alkaline Earth Metals: – Group 2– Harder, denser, and stronger than alkali metals
• Transition Metals: – Group 3-12– Form positive ions, reactive, make coloured
compounds
• Metalloids: – On staircase between metals and non-metals– Exhibits properties of both
• Halogens: – Group 17; Reactive non-metals– Electron deficient and readily share electrons
with other elements
• Noble Gases:– Group 18– Do not react chemically with other materials
and cannot be absorbed– Valence shell full
The Periodic Table & Electrons• Periodic trends are linked to the way electrons
fill energy levels.
• Remember that for each proton there is one electron in an atom, therefore as the atomic number increases, so does the number of electrons.
• To understand trends, we use the Bohr-Rutherford Model of the atom.
The Bohr-Rutherford Model
• Electrons in energy levels• 2 in first level• 8 in other levels
• What element is this?• Sodium, Na
• Group Related Pattern:
– All the elements in a group have the same number of valence electrons.
– The old number system – The roman numeral is the same as the number of valence electrons.
– The new system – The last digit of the number is the number of valence electrons.
• Period-Related Pattern
Period Number = Number of Energy Levels
3.2 Physical Properties
• Ionization energy• Electronegativity• Atomic Radii • Ionic Radii
• Across period 3 & down group 1 & 17
More Trends – Worksheet• Ionization Energy: The energy required to
remove one valence electron from an atom.
• Electronegativity: How strongly an atom attracts the electrons in a covalent bond
• Atomic Radius:The distance from the nucleus to the valence electron shell of an atom
• Ionic Radius: The distance from the nucleus to the valence electron shell of an ion
Ionization energy vs. atomic numberIonization energy vs. atomic number
CaK
H
He
Li
BBe C
N O
F
Ne
Na
MgAl
SiP S
Cl
Ar
0
500
1000
1500
2000
2500
0 2 4 6 8 10 12 14 16 18 20
Element
Ioni
zatio
n en
ergy
(kJ/
mol
)
Electronegativity Trend
Atomic radius vs. atomic numberAtomic radius vs. atomic number
Ca
K
H He
Li
BBe
C N O FNe
NaMg
Al Si P S ClAr
0
50
100
150
200
250
0 2 4 6 8 10 12 14 16 18 20
Element
Atom
ic R
adiu
s (p
m)
Atomic Radius & Ionic Radius
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/atomic4.swf
3.3 Chemical Properties• Group Properties:
– Alkali metals with water– Alkali metals with halogens– Halogens with water– Halogens with halide ions
• Oxides of period 3 properties– Ionic vs. covalent bonding nature– Basic vs. acidic nature– Industrial processes
Alkali metals with H2O
• M + H2O MOH + H2
• Trend:Very reactive; increasing down group• Observations:
– Highly exothermic – heat & light– Fizzing of hydrogen gas formed
– Video
Halogens with H2O
• Reactivity decreases down group because electronegativity and oxidizing power decreases down group; electrons farther from nucleus and are shielded
• Halogens General Video
Halogen and halide ions
Higher Halogen displaces lower halogen from salt; never other way around!
•Cl2 + I- Cl- + I2
•Cl2 + Br- Cl- + Br2
•Br2 + I- Br- + I2
•Br2 + Cl- No rxn
•I2 + Cl- No rxn
•I2 + Br- No rxn
Halogen and metal
• Make salts with halide ion• Salts are usually white in colour and soluble
in water creating colourless solutions• Common insoluble halides: silver and lead
Things to Know:• Ionic compound– attraction of ions creates bond• Covalent compound – shared electrons create
bond• Polar Covalent – a covalent bond where
electrons are not shared equally creating positive and negative “ends” on the bond
• Acidic – having a pH of less than 7; H+• Basic – having a pH of more than 7; OH
Oxides:
• Compounds containing at least one oxygen atom
• Bonded with metal: ionic compound & basic• Bonded with non-metal: polar covalent
compound; polarity decreasing across period & acidic (increasing across period)
• **aluminum oxide is amphoteric – reacts with acid and base**