explain electron afinity,electronegativity electron positivitity and metal and non metal How there properties vary in a group and period
Answers
Explanation:
The higher the electronegativity of an atom, the greater its ability to attract shared electrons. The electronegativity of atoms increases as you move from left to right across a period in the periodic table. The electronegativity of atoms decreases as you move from top to bottom down a group in the periodic table.
Atoms become more electronegative across a period due to the increase in Zeff (effective nuclear charge). The number of protons increases across the period, yet the amount of shielding does not increase, leading to increased electronegativity. Explain the decrease in electronegativity down a group.
The elements in the periodic table are arranged in order of increasing atomic number. All of these elements display several other trends and we can use the periodic law and table formation to predict their chemical, physical, and atomic properties. Understanding these trends is done by analyzing the elements electron configuration; all elements prefer an octet formation and will gain or lose electrons to form that stable configuration.
Atomic Radius
We can never determine the atomic radius of an atom because there is never a zero probability of finding an electron, and thus never a distinct boundary to the atom. All that we can measure is the distance between two nuclei (internuclear distance). A covalent radius is one-half the distance between the nuclei of two identical atoms. An ionic radius is one-half the distance between the nuclei of two ions in an ionic bond. The distance must be apportioned for the smaller cation and larger anion. A metallic radius is one-half the distance between the nuclei of two adjacent atoms in a crystalline structure. The noble gases are left out of the trends in atomic radii because there is great debate over the experimental values of their atomic radii. The SI units for measuring atomic radii are the nanometer (nm) and the picometer (pm). 1 nm = 1 X 10-9 m; 1 pm = 1 X 10-12 m.
The elements in groups 3-12 are called transition elements, or transition metals. Similar to the main-group elements described above, the transition metals form positive ions but due to their capability of forming more than two or more ions of differing charge, a relation between the group number and the charge is non-existent.
Problems
1. Arrange these elements according to decreasing atomic size: Na, C, Sr, Cu, Fr
2. Arrange these elements according to increasing negative E. A.: Ba, F, Si, Ca, O
3. Arrange these elements according to increasing metallic character: Li, S, Ag, Cs, Ge
4. Which reaction do you expect to have the greater cell potential?
A) 2Na(s) + Cl2(g)→ 2NaCl(s) or 2Cs(s) +Cl2(g) → 2RbCl(s)
B) 2Na(s) + Cl2(g)→ 2NaCl(s) or Be(s) + Cl2(g) → BeCl2(s)
5. Which equation do you expect to occur?
A) I2(s) + 2Br (aq) → Br2(l) + 2I(aq)
B) Cl2(g) + 2I (aq) → I2 (s) + 2Cl(aq)
Answers
1. Fr, Sr, Cu, Na, C
2. Ba, Ca, Si, O, F
3. Li, S, Ge, Ag, Cs
4. A) Second equation
B) First equation
5. A) Yes
B) No
External Links
The History of the Periodic Table- Part 1 of 2
The Element Song
Groups of the Periodic Table
Periodic Trends
Periodic Trends
Problems
*Highlight Answer:_____ to view answers.
1. An element that is an example of a metalloid is (a) S; (b) Zn; (c) Ge; (d) Re; (e) none of these
Answer: (c) Ge
2. In the periodic table, the vertical (up and down) columns are called (a) periods; (b) transitions; (c) families/groups; (d) metalloids; (e) none of these.
Answer: (c) families/groups
3. Why are noble gases inert (nonreactive)?
Answer: Noble gases are inert because they already have a full valence electron shell and have little tendency to gain or lose electrons.
4. What are compounds that contain a halogen called?
Answer: Salts
5. Lanthanides and Actinides are: (a) alkali earth metals; (b) transition metals; (c) metalloids; (d) alkali metals; (e) none of these
Answer: (b) transition metals
References
Cotton, F.A.; Wilkinson, G. (1988). Advanced Inorganic Chemistry (5th Edn). New York: Wiley. ISBN 0-471-84997p. 1385.
Hutchinson, John. "Journal of Chemical Education." Concept Development Studies in Chemistry (2007). Print. Outside Links
Jolly, William L. (1991). Modern Inorganic Chemistry (2nd Edn.). New York: McGraw-Hill. ISBN 0-07-112651-1.
Petrucci, Ralph H. General Chemistry. 9th ed. New Jersey: Pearson Prentice Hall, 2005.
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Periodic Trends of Elemental Properties Periodic Trends
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