Question 1

Which of the following best explains why the 4s orbital fills before the 3d orbital in electron configurations for the first 38 elements?

Accepted Answer

Because the 4s orbital has a lower energy than the 3d orbital, so electrons fill the lowest available energy level first.

Question 2

What is the complete electron configuration for the element iron (Fe, atomic number 26)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^6$$

Question 3

Which statement about the periodic table and electron configurations is CORRECT?

Accepted Answer

The s and p sublevels always correspond to the row number, while the d sublevel is one less than the row number.

Question 4

Which of the following is the correct electron configuration for bromine (Br, atomic number 35)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^5$$

Question 5

Which of the following best describes an atomic orbital?

Accepted Answer

A region in space with a high probability of finding an electron.

Question 6

Which element has the following electron configuration: $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^5$$?

Accepted Answer

Chlorine (Cl)

Question 7

Why did Dmitri Mendeleev receive credit as the 'father of the modern periodic table' over his predecessors?

Accepted Answer

He arranged elements by increasing atomic mass and chemical reactivity, left gaps for undiscovered elements, and accurately predicted their properties.

Question 8

Which of the following is TRUE about the filling order of electron sublevels for the first 38 elements?

Accepted Answer

The 4s sublevel fills before the 3d sublevel.

Question 9

How many electrons can the d sublevel hold, and how is this reflected in the periodic table?

Accepted Answer

It can hold 10 electrons, reflected by the 10 columns in the d-block.

Question 10

Which of the following statements about orbital shapes is correct?

Accepted Answer

S orbitals are spherical and increase in size with higher energy levels.

Question 11

A patient is exposed to a new element. Its electron configuration ends in $$4p^2. $$Based on this, which element is it?

Accepted Answer

Germanium (Ge) is $$4p^2$$, so the element is Germanium.

Question 12

Which of the following is the correct order of sublevel filling after $$3p^6$$?

Accepted Answer

$$4s^1$$

Question 13

Which of the following best describes the historical significance of Mendeleev's predictions?

Accepted Answer

He predicted the existence and properties of elements that were later discovered, such as germanium.

Question 14

If an element has the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^6$$\ $$5s^2$$, what is the atomic number of this element?

Accepted Answer

36

Question 15

Which of the following is a consequence of Heisenberg’s Uncertainty Principle as it relates to atomic orbitals?

Accepted Answer

We can only describe regions where electrons are likely to be found, not their exact paths.

Question 16

Which of the following electron configurations represents a noble gas?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$

Question 17

Which of the following best explains why helium is placed in the noble gas column, even though its electron configuration is $$1s^2$$?

Accepted Answer

Because its chemical properties match those of the noble gases, which are non-reactive gases at room temperature.

Question 18

Which of the following is the correct electron configuration for strontium (Sr, atomic number 38)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^6$$\ $$5s^2$$

Question 19

Which of the following is a real-world application of understanding electron configurations?

Accepted Answer

Predicting the chemical reactivity and bonding behavior of elements in pharmaceuticals.

Electron Configurations and the Structure of the Periodic Table

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