Periodic Trends

Atomic radiusIonic radius

ElectronegativityIonization energy

Your tool box• # protons• Effective nuclear charge• # electrons• # of energy levels• electron repulsion• Core electrons/electron shielding• F (coulomb’s law)• q (coulomb’s law)• r (coulomb’s law) – usually deals with # of energy

levels

Explain why the radius of the chlorine atom is smaller than the radius of the chloride ion, Cl-.

(Radii : Cl atom = 0.99Å; Cl- ion = 1.81 Å)

Now write an explanation using the tools selected

• # protons• Effective nuclear charge• # electrons• # of energy levels• electron repulsion• Core electrons/electron shielding• F (coulomb’s law)• q (coulomb’s law)• r (coulomb’s law) – usually deals with # of energy

levels

Chlorine and chloride have the same number of protons (17), but they have different numbers of electrons (chlorine has 17 while chloride has 18). The increase in electrons causes more electron repulsion, increasing the radius of chloride.

Tips

• Make sure to mention things that are in common and things that are different (example to follow)

• Use tool box words whenever possible• Mention both substances and use specific

facts (# of protons, electrons, energy levels, etc.)

Tool box words you think are important

• Common • Different

Tool box words you think are important

• Common– Same number of

protons/ENC

• Different– # of electrons– Electron repulsion

Explain the fact that Calcium’s first ionization energy is larger than potassium’s.

Now write an explanation using the tools selected

• # protons• Effective nuclear charge• # electrons• # of energy levels• electron repulsion• Core electrons/electron shielding• F (coulomb’s law)• q (coulomb’s law)• r (coulomb’s law) – usually deals with # of energy

levels

• Potassium and calcium have the same number of core electrons, but calcium has one additional proton. The larger nucleus means an increased effective nuclear charge. Since the large nuclear charge on calcium increases the force of attraction between the nucleus and the valence electron according to coulomb’s law, more energy is required to remove the electron from calcium.

Homework Answers

1. Rotate around the group sharing answers to the homework (#3 starts)

2. If there are any you can’t come to consensus on, please let me know

Today, we’re writing and talking….

First, we’re writing….

We have 5 examples that you will write explanations for

Your tool box• # protons• Effective nuclear charge• # electrons• # of energy levels• electron repulsion• Core electrons/electron shielding• F (coulomb’s law)• q (coulomb’s law)• r (coulomb’s law) – usually deals with # of energy

levels

Which is larger: nitride or oxide? Explain why.

Now write an explanation using the tools selected

• # protons• Effective nuclear charge• # electrons• # of energy levels• electron repulsion• Core electrons/electron shielding• F (coulomb’s law)• q (coulomb’s law)• r (coulomb’s law) – usually deals with # of energy

levels

Nitride vs Oxide

• Nitride and oxide are isoelectronic (they have the same number of electrons – core and valence); however, the larger nucleus on oxide (8 protons for oxide while only 7 protons for nitride) means a larger force of attraction between the valence electrons and the nucleus, reducing the atomic radius of oxide.

Predict how the first ionization energy of Na compares to that of Li. Justify.

Now write an explanation using the tools selected

• # protons• Effective nuclear charge• # electrons• # of energy levels• electron repulsion• Core electrons/electron shielding• F (coulomb’s law)• q (coulomb’s law)• r (coulomb’s law) – usually deals with # of energy

levels

Predict how the first ionization energy of Na compares to that of Li.

Sodium’s valence electron is in the 3rd energy level while Lithium’s valence electron is in the 2nd energy level. The ionization energy of Na would be less than that of Li because the electron that would be removed is further from the nuclear charge. Also, the increased number of core electrons creates more electron shielding, making the valence electron easier to remove. Coulomb’s law indicates that electrons further from the nucleus have a lower attractive force holding them to the nucleus, so once again less energy is required to remove the electron from Na.

The radius of the Ca atom is larger than the radius of the Ca ion. Explain.

Now write an explanation using the tools selected

• # protons• Effective nuclear charge• # electrons• # of energy levels• electron repulsion• Core electrons/electron shielding• F (coulomb’s law)• q (coulomb’s law)• r (coulomb’s law) – usually deals with # of energy

levels

The radius of the Ca atom is larger than the radius of the Ca ion.

• Calcium atom and calcium ion both have 20 protons, but calcium has 20 electrons on 4 energy levels while the calcium ion has only 18 electron on 3 energy levels. The ion is smaller than the atom because the increased ENC (while decreasing the electron shielding due to fewer core electrons) pulls the smaller number of electrons closer to the nucleus.

Predict how the first ionization energy of Na compares to that of Ne. Explain your reasoning.

The effective nuclear charge of Ne is much higher than Na (+8 compared to +1). Additionally, Na’s valence electron is found on the 3rd energy level, while Ne’s is on the 2nd energy level, meaning that neon is much smaller than sodium. Coulomb’s law says that electrons closer to the nucleus have a greater force of attraction, therefore more energy is required to remove the valence electron.

Predict how the first ionization energy of Na compares to that of Ne.

The electronegativity of F is larger than that of Cl.

(For more information on electronegativity, click this link http://www.chemguide.co.uk/atoms/bonding/electroneg.html)

Now write an explanation using the tools selected

• # protons• Effective nuclear charge• # electrons• # of energy levels• electron repulsion• Core electrons/electron shielding• F (coulomb’s law)• q (coulomb’s law)• r (coulomb’s law) – usually deals with # of energy

levels

The electronegativity of F is larger than that of Cl.

While they both have the same effective nuclear charge (+7), fluorine is smaller, meaning the shared electron is closer to the nucleus. There is a greater force of attraction, according to coulomb’s law, when the electron is closer to the nucleus.

Now, we’re talkingQuiz your face partner using the blue cards

Disclaimer: I made these a few years ago, so they don’t mention coulomb’s law. Please feel free to

supplment the answers on the back

Practice Quiz• You will turn this quiz into me (but it will not

count as a grade)• Write your name and class period on top of

the lined side of the notecard; start on the lined side and answer this question:

Which atom has a higher ionization energy, Al or Si? Explain why.