Understanding Effective Nuclear Charge, Atomic Size, and Electron Affinity
This text explores the concepts of Effective Nuclear Charge (ENC) and its impact on atomic size and electron affinity. As ENC increases, atomic size decreases, leading to tighter electron clouds. Conversely, electron affinity decreases with a decrease in ENC. The text also examines trends in atomic size down a family in the periodic table, noting that additional electron layers lead to larger atoms. Additionally, it compares ENC and ionization energy across specific elements and assesses which atoms are most likely to form negative ions based on their valence electrons.
Understanding Effective Nuclear Charge, Atomic Size, and Electron Affinity
E N D
Presentation Transcript
If ENC increases, size _____ • Size decreases • ENC pulls the electrons in tighter, therefore the total size of the atom (created by the electron cloud) is smaller
What happens to Electron Affinity as ENC decreases • Electron Affinity decreases as ENC decreases • Electron Affinity is the change in energy as an atom gains an electron • If an atom “wants” an electron more (higher ENC), it will release more energy when it gains the electron
Why do atoms get larger as you go down a family? • There are the same number of valence electrons, so they all have approximately the same ENC • As you go down a period, an extra layer of electrons are added (you increase energy levels) • Extra energy levels need space, so the atom gets bigger
Which element has the highest ENC – Si, I, Mg, Al? • ENC ~ # valence electrons • I has 7 valence electrons – ENC ~ 7 • Si has 4 valence electrons – ENC ~ 4 • Al has 3 valence electrons – ENC ~ 3 • Mg has 2 valence electrons – ENC ~ 2
Which element has the highest ionization energy – Se, Ba, Rb, Cl • Higher ENC -> higher IE • Se has 6 valence electrons – ENC ~ 6 • Ba has 2valence electrons – ENC ~ 2 • Rb has 1 valence electrons – ENC ~ 1 • Cl has 7 valence electrons – ENC ~ 7
Which atom will become a negative ion easiest – O, Xe, Ca, Li • O has 6 valence electrons, wants 2 more, has the best electron affinity • Xe has a higher ENC, but has 8 valence electrons and wants no more
