Gsci 163
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GSCI 163. Lecture 5. Review. Electrons in an atom are distributed in shells, orbitals and energy levels. When electrons absorb photons they jump to higher orbitals They move back up by emitting a photon whose energy correspond to the change in energy level. Activity.

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GSCI 163

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Gsci 163

GSCI 163

Lecture 5


Review

Review

  • Electrons in an atom are distributed in shells, orbitals and energy levels.

  • When electrons absorb photons they jump to higher orbitals

  • They move back up by emitting a photon whose energy correspond to the change in energy level


Activity

Activity

  • Finding the emission lines of different compounds.


Chemistry

Chemistry

  • Electrons in an atom are distributed in shells, orbitals and energy levels.

  • The way electrons are shared will determine how elements combine with each other to form compounds.

  • The highest or last shell of an atom is the valence shell

  • The valence shell determines the chemistry and properties


The periodic table

The periodic table


Various groups

Various groups

  • Metals and non-metals

    • Metals tend to lose electrons in chemical reactions

    • Non-metals tend to gain (or share) electrons in chemical reactions

Semi-metals have both metallic and non-metallic properties

  • Most reactive metal  Cesium

  • Most reactive non-metal  Fluorine


Noble gases

Noble gases

  • The valence shell is full. Thus they almost never react.

    • Argon gas (Ar) is used as an inert gas in light bulbs to prevent the filament, made of tungsten (W), from reacting under intense heat


Other families

Other families

  • Alkali metals

    • Only one valence electron; very soft metals

    • React so easily with Oxygen (O) and moisture that they need to be stored under oil

  • Alkaline earth metals

    • Two valence electrons; harder than alkali metals

    • Not so reactive.

  • Halogens

    • Seven electrons in the valence shell

    • Very active non-metals

      • Fluorine – highly corrosive,

      • Chlorine – purifying agent,

      • Bromine – desinfectant

  • Semi-metals (semi-conductors)

    • 3,4 or 5 electrons in the valence shell

    • Makes them behave both as metals and insulators


Atomic size

Atomic size

  • Increase when:

    • Add a new shell (moving down a group) since electrons are farther away from the nucleus

    • Number of protons decrease (across a period) since electrons are more loosely bound by electrostatic force

He ~ 0.064 nm

Cs ~ 0.47 nm


Ionization energy

Ionization energy

  • Energy required to remove one electron from the outer shell

Hardest elements to remove one electron from

He

H


Octet rule

Octet rule

  • Most common elements have electrons on the s and porbitals of their outmost shells

  • We can fit 2 electrons on s and 6 on p, with a total of 8 electrons

    Octet rule: atoms will combine with other atoms in such a way that gives a full shell of 8 electrons


Naming compounds

Naming compounds

  • We represent compounds with a chemical formula:

    H2O

  • Names are also used to identify the compound unambiguously

Symbol of the element

Number of atoms of the element


Compounds with special names

Compounds with special names

There are no rules for these. Their names are learned individually


Metal and a non metal

Metal and a non-metal

  • Groups 1A, 2A plus Aluminum (Al), Zinc (Zn) and Silver (Ag). They form only one ion.

  • Rule for binary compounds:

    • Name of the metal + non-metal with ending –ide

      Examples:

      NaCl – Sodium Chloride

      Al2O3 –

      Ca3N2 –


Two non metals

Two non-metals

  • Rule:

    • The less metallic element (farther left and/or farther down the periodic table) comes first. The second is named with ending –ide .

    • For more than one element use Greek prefixes: di(2), tri(3), tetra(4), penta (5), hexa (6), hepta (7), octa (8).

      Examples:

      HCl – hydrogen chloride

      CS2 –

      PBr3 –

      IF7 –


Compounds with polyatomic ions

Compounds with polyatomic ions

  • Metal plus a polyatomic ion:

    Rule: name of the metal + the name of

    of the polyatomic ion

    Example:

    ZnSO4 – Zinc Sulfate

    NaC2H3O2 –

    Mg(NO3)2 –

    K3PO4 –


Next class

Next class

Calculating reactions

  • To prepare for the class read:

    • Handout pages 17 to 20 (day 5)

    • Presentation by Rebecca Cross, Acids and Bases

  • To prepare for the quiz read:

    • Handout pages 16 (day 4)

    • Power point for this class

    • Your class notes


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