Chapter 9

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Published on 16 Oct 2011
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Chapter 9: the periodic Table and Some Atomic Properties
- The basis of the PT is the e’ configuration of the element s
9-1 classifying elements: the Periodic law and the PT:
Periodic law: when elements are arranged in order of increasing atomic mass,
certain sets of properties recur periodically
- Molar volume: atomic mass of an element divided by the density of its solid form
- Periodic law was based on molar volume ( atomic volume)
- Results represented by a graph of atomic volume against atomic mass ( molar
volume against atomic number)
- Argon was the first noble gas discovered
- Restated periodic law: similar properties recur periodically when elements are
arranged according to increasing atomic number
- Page 343 description of periodic table!
9-2 metals and non-metals and their ions:
- Metals good conductors of heat/electricity, malleable, ductile, moderate-high MP
- Non-metals non-conductors of heat/electricity , non-malleable, brittle solid or gas
at room temp
- Metalloids look like metals, behave like metals but have some non-metallic
properties as well
- Physical and chemical properties of elements are determined largely by its e’
config, valence electronic shell
Noble gases:
- Atomics of the noble gases have the max # of e’ permitted in the valence shell
- The s block , Al tend to lose enough electrons to acquire the e’ config of the noble
gases
Main-group metal ions:
- Al is the only p-block metal that forms an ion with a noble gas config Al3+
Main-group non-metal ions:
- Atoms of group 17 & 16 the most active non-metals
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- Non-metals will gain a single e spontaneously , but energy is required to force it to
accept more than one
- Necessary energy is often supplied by: attraction between positive and negative
ions
Transition metal ions:
- Electron config for: Ti [Ar] 3d24s2 Ti2+ [Ar]3d2
- E’ config with half-filled or filled d or f sub shells have a special stability
9-3 sizes of atoms and ions:
Atomic radius:
- The probability of finding an electron decreases with increasing distance from the
nucleus, but no where does the probability falls to zero.
- Effective atomic radius: distance from the nucleus within 95% of all the electron
charge density found
- Covalent radius: one half the distance between the nuclei of two identical atoms
joined by a single covalent bond
- Ionic radius: based on the distance on the distance between the nuclei of ions joined
by an ionic bond
- Metallic radius: one half the distance between the nuclei of 2 atoms in contact in
the crystalline solid metal
- In a solid sample of noble gas, the distance between the centers of the
neighbouring atomic called van del waals radius
1nm=1 * 10-9 m; 1pm = 1* 10-12 m; 1nm= 1000pm
Screening and penetration:
- Penetration was described as a gauge of how close and e’ gets to the nucleus
- S e’ with their extra humps of probability close nuclear penetrate better than d e’
- Screen or shielding reflects how an outer e’ is blocked from the nuclear charge by
the inner e’
- The core e’ shield the outer shell e’ from the full attractive force of the nucleus
- Effective nuclear charge Zeff
Zeff=Z - S S= # of inner e’ that shield an outer e’
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