Chapter 6 Periodic Trends

Grouping Elements _______: horizontal rows. _______: vertical columns. Elements in a period show no similarity in chemical properties. _______: vertical columns. Elements in a family have similar chemical properties and predictable trends in physical properties.

Grouping Elements We give some groups names IA are the :______________ IIA are the :______________ VIIA are the :______________ VIIIA are the :______________

Metals and Nonmetals ___________ are shiny, good conductors of heat and electricity, malleable, ductile, and form cations (positive ions) by losing electrons during chemical change. ___________ are not shiny. They are poor conductors and are brittle. They form anions (negative ions) by gaining electrons during chemical changes. ___________ have some characteristics of both metals and nonmetals. They are B, Si, Ge, As, Sb, Te, Po, At.

State of Matter Some elements are gases at room temperature: How many are liquids? Which ones?— the rest are solids.

What Is The… symbol of the noble gas in period 3? lightest element in Group IVA? only metalloid in Group IIIA? element whose atoms contain 18 protons? How many neutrons do these atoms have? element in period 5, Group VIIA name, atomic number and atomic mass for Mg?

For Ca, K, Cu, Zn, Si & Kr : which are metals? which are transition metals? which tend to form positive ions? which are noble gases? which are metalloids? which develop ions with a charge of -1? which are halogens?

Let’s do some electron configurations

Abbreviated electron configuration 2He 10Ne 18Ar 36Kr These configurations are for ground state configurations--lowest energy.

Valence Electrons Valence electrons are the electrons located in the _________ orbitals. They are involved in forming chemical bonds. For “A Family” elements the number of valence electrons in an atom = Don’t worry about inner core of electrons (smaller n) since these are filled levels and don’t enter into bond formation ( for A groups)

What is the “determining e-” for: P Bi Sr Te I Cs

The Octet Rule Extra stability occurs when an atom or ion has ??? electrons in the outermost energy level (2 or 0 for the first period). This mimics the electron configuration of the _____. The ????? are sometimes called inert because they do not form ions or chemical bonds.

Ion Formation Group IA ns1 Group IIA ns2 Group IIIA ns2np1 Loses Group IIA ns2 Group IIIA ns2np1 Group IVA ns2np2 Group VA ns2np3 Gains Group VIA ns2np4 Group VIIA ns2np5 Group VIIIA ns2np6 For cations: name of element plus ion For anions: replace the last syllables of the element name by --ide + ion.

Transition metal cations No simple rules as for A groups Cu+, Cu2+ Fe2+, Fe3+ Au+, Au3+

What is the “determining e- for: Li+ Be2+ B3+ N3- O2- H- F- H+

What’s the ion formed by: P Ba S N I Cs

Isoelectronic Atoms or ions F- [He] 2s2 2p6 O2- [He] 2s2 2p6 Name a cation isoelectronic with O2-

Which of the following pairs are isoelectronic? Cl-, Ar Na+, Ne Mg2+, Na+ Li+, Ne O2-, F-

Atomic Radius Think of an atom as a sphere whose radius is determined by the location of the e- furthest from the nucleus. Trends within families and periods: The larger value of n for a family, the larger the atomic radius. Size __________ from top to bottom in a family. Within an energy level, the larger the number of protons in the nucleus, the smaller the atomic radius. Size ___________ from left to right within a period.

Arrange according to increasing atomic size: Al, S, P, Cl, Si In, Ga, Al, B, Tl Sr, Ca, Ba, Mg, Be P, N, Sb, Bi, As Na, K, Mg

Ionic Radius Within a family, size __creases Size of parent to cation: Parent is ??? than cation Size of parent to anion: Parent is ???? than anion Note for period 3: N3- > O2- > F- > Na+ > Mg2+ > Al3+ Most positive ion the smallest, most negative the largest

Ionic Radius Which is smaller? Cl or Cl- Na or Na+ O2- or S2- Mg2+ or Al3+ Au+ or Au3+ P, P3-, or P5+

Ionization energy Minimum energy required to remove an ??? from a ground-state atom Always positive (requires energy) Measures how “tightly” the determining e- is held by the atom (think size also) Is greater for smaller radius atoms

Trends in ionization energy The larger value of n for a family, the smaller the ionization energy. Ionization energy __________ from top to bottom in a family. Within an energy level, the larger the number of protons in the nucleus, the larger the ionization energy. Ionization energy ___________ from left to right within a period.

Trends in ionization energy

Arrange in order of increasing Ionization Energy: N, O, F Li, K, Cs Cl, Br, I He, Ne, Ar

Electron affinity Electron affinity is the energy change when an e- is added to a ground-state atom. Energy associated with this reaction: Positive electron affinity means that energy is released, e- addition is favorable and anion is stable! Negative electron affinity means that energy is required, e- addition is unfavorable and anion is stable! First EA’s mostly positive, a few negative

Trends in electron affinity The larger value of n for a family, the smaller the electron affinity. Electron affinity __________ from top to bottom in a family. Within an energy level, the larger the number of protons in the nucleus, the larger the electron affinity. Electron affinity ___________ from left to right within a period. Nonmetals are more likely to accept e-s than metals. Halogens accept e-s most readily.