Question

1. How many electrons are in ₂₀⁴⁰ Ca⁺ ?

2. How many moles are in 40.00 oxygen has (O₂)?

3. What is the energy in kJ/mol, of a mole of photons with wavelength 494 nm?

4. Particle with a mass 9.1 * 10^-31 kg has an uncertainty in position of .54 nm. What is the velocity in km/s?

5. Electron configuration to Co: [Ar] 3d^? 4s²_. How many unpaired of 3d electrons are there in Co?

6. Which has the greatest effective nuclear charge Se or Br? And how?

7. Ionization energy decreases as you descend a group. Why?

Answer 1

Q.6) Br has the greatest effective nuclear charge.

The periodic table tendency for effective nuclear charge: Increase across a period (due to increasing nuclear charge with no accompanying increase in shielding effect).

Q.7 ) as one progresses down a group on the periodic table, the ionization energy will likely decrease since the valence electrons are farther away from the nucleus and experience greater shielding. They experience a weaker attraction to the positive charge of the nucleus.