College

5. What is the correct arrangement of the first seven energy levels in an atom?

A. [tex]1s, 2s, 2p, 3s, 3d, 4s[/tex]
B. [tex]1s, 2p, 2s, 3p, 3d, 4s[/tex]
C. [tex]1s, 2s, 3s, 4s, 3d[/tex]
D. [tex]1s, 2p, 2s, 3s, 4s, 3d[/tex]

6. How many electrons does an atom of the element "X" have in its p-subshell?

A. 5
B. 7
C. 9
D. 10

7. How many peaks would be produced in the mass spectrum of the three isotopes of oxygen ([tex]^{16}[/tex]O, [tex]^{17}[/tex]O, [tex]^{18}[/tex]O)?

A. 1
B. 3
C. 5
D. 6

8. The decreasing metallic character across a period is due to:

A. Decreasing electron affinity
B. Increasing ionization energy
C. Decreasing ionization energy
D. Increasing atomic size

Answer :

Sure, let's go through each part of the question step-by-step:

1. Correct Arrangement of Energy Levels:

The correct order for electron filling in an atom follows the Aufbau principle:
- 1s
- 2s
- 2p
- 3s
- 3p
- 4s
- 3d

None of the options seem to completely match this exact order, but we're focusing on highlighting the correct filling sequence for better understanding.

2. Electrons in the p Subshell for Element X:

In atoms, the p subshell can hold a maximum of 6 electrons. If we assume that the element X has completely filled its p subshells as allowed by the natural order:
- 2p holds 6 electrons
- 3p can hold up to 6 electrons

If element X fills its p subshell up to a typical level for elements known in the periodic table, we’ll have 10 electrons in the p subshell:

Therefore, the correct number of electrons in the p subshell is 10.

3. Mass Spectrum Peaks for Oxygen Isotopes:

Oxygen has three common isotopes:
- [tex]\(^{16}O\)[/tex]
- [tex]\(^{17}O\)[/tex]
- [tex]\(^{18}O\)[/tex]

Each of these isotopes will appear as a separate peak in a mass spectrum. This means there will be three peaks corresponding to the three isotopes of oxygen.

Thus, the correct number of peaks is 3.

4. Reason for Decreasing Metallic Character Across a Period:

As you move from left to right across a period in the periodic table, the following trends are observed:
- Ionization energy increases because additional electrons are added to the same energy level while the nuclear charge increases, making it harder to remove an electron.
- Atomic size generally decreases which contributes indirectly to increasing ionization energy.

Therefore, the decreasing metallic character across a period is primarily due to increasing ionization energy.

To summarize:
- The number of electrons in the p subshell for element X is 10.
- The mass spectrum of oxygen would produce 3 peaks.
- The decreasing metallic character across a period is due to increasing ionisation energy.