Unit Test 4

CHEMISTRY TEST #4: Periodic Trends & Electron Configurations


Vocabulary:


Orbital - a region of space around the nucleus that contains 90% of the electron locations

  • You can never determine exactly where an electron is

Orbit - Based on the Bohr model, the movement of electrons around the nucleus

Electronegativity - the measurement of an element’s ability to attract a shared pair of electrons in a chemical bond

Ionization - the minimum energy required to remove an electron from the valence shell of a neutral atom or molecule

Atomic Size - a measure of an atom’s radius, defined as the distance between the nucleus to its outermost electron shell




Concepts and skills:


Double Slit Experiment

  • What did it demonstrate?

    • That electrons functioned as both a particle and a wave

  • What was it?

    • Thomas Young fired electrons at a screen with two slits and discovered that even when firing one at a time a dual wave pattern occurs 

Write an electron configuration

  • Long method 

    • Sr: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2

  • Short cut method (with noble gases)

    • Sr: [Kr] 5s2

  • Box method

    • Do Sr. on paper

  • Exceptions 

    • Cr, Mo, Cu, Ag

    • Cr: [Ar] 4s1, 3d5

    • Mo: [Kr] 5s1, 4d5

    • Cu: [Ar] 4s1, 3d10

    • Ag: [Kr] 5s1, 3d10

Periodic Trends

  • Atomic radius/size

    • Trend: Left to right gets smaller, Up to down gets smaller

      • Fr is the biggest, He is the smallest

  • Ionization energy

    • Trend: Opposite of atomic size and equal to electronegativity 

      • Fr is the least ionized, He is the most ionized 

  • Electronegativity (ignore noble gases)

    • Trend: Opposite of atomic size and equal to ionization energy

      • Fr is the least electronegative, He is the most electronegative

  • Isoelectronic series 

    • Trend: Goes up or down depending on how many electrons are added/taken away to equal the nearest noble gas

    • Ne: N3-, O2-, F-, Na+, Mg,2+, Al3+

    • Electrons with 4 valence electrons are the mid point 

      • They don't go either way

    • ie. P has 5 valence electrons so it would rather gain 3 to be even with argon than lose 5 to be even with neon