Question

Two representative elements are in the same period of the periodic table. Which statement correctly describes the atoms of the two elements?(1 point)
They have the same number of valence electrons.
They have the same number of valence electrons.

They have valence electrons in different energy levels.
They have valence electrons in different energy levels.

They have valence electrons in the same energy level.
They have valence electrons in the same energy level.

They have the same number of electrons.Helium is in group 18 of the periodic table. How is helium different from the other elements in this group?(1 point)Helium atoms have valence electrons in the first energy level, while atoms of the other elements in the group have valence electrons in the second energy level.
Helium atoms have valence electrons in the first energy level, while atoms of the other elements in the group have valence electrons in the second energy level.

Helium atoms have 2 valence electrons, while atoms of the other elements in the group all have 8 valence electrons.
Helium atoms have 2 valence electrons, while atoms of the other elements in the group all have 8 valence electrons.

Helium atoms have a full outer energy level, while atoms of the other elements in the group do not have a full outer energy level.
Helium atoms have a full outer energy level, while atoms of the other elements in the group do not have a full outer energy level.

Helium atoms have 2 electrons, while atoms of the other elements in the group all have 18 electrons.
Use the periodic table to answer the question.
Which element has atoms with valence electrons in a higher energy level than those of calcium (Ca)?
lithium (Li)
lithium (Li)

cesium (Cs)


bromine (Br)

oxygen (O)
Use the periodic table to answer the question.
Which statement best describes the arrangement of electrons in an atom of fluorine (F)?
There are seven electrons in the first energy level and two electrons in the second energy level.
There are seven electrons in the first energy level and two electrons in the second energy level.

There are five electrons in the first energy level and two electrons in the second energy level.
There are five electrons in the first energy level and two electrons in the second energy level.

There are two electrons in the first energy level and seven electrons in the second energy level.
There are two electrons in the first energy level and seven electrons in the second energy level.

There are two electrons in the first energy level and five electrons in the second energy level.

Answer 1

1) They have valence electrons in the same energy level.

2) Helium atoms have 2 valence electrons, while atoms of the other elements in the group all have 8 valence electrons.

3) cesium (Cs)

4) There are two electrons in the first energy level and seven electrons in the second energy level.

In the periodic table, elements are arranged in order of increasing atomic number into groups and periods.

In the periodic table, we have an arrangement of atoms based on their respective groups and periods.

If I pick two representative elements in the same period, their number of valence electrons will differ by 1 but they will all be accommodated in the same energy level.

Helium is the first member of group 18. Unlike the other members of the group, its first shell is also its valence shell. It has two and not eight valence electrons like other members of the group.

The electronic configuration of Ca is [Ar] 4s², that of Li is [He] 2s1, that of Cs is [Xe] 6s1, that of Br is [Ar] 4s² 3d¹⁰ 4p⁵ and that of oxygen is [He] 2s² 2p⁴.

We can see that only Cs has  valence electrons in higher energy orbitals than those of Ca.

Lastly, Fluorine is in group 17. There are nine electrons in this atoms. They arranged in such a way that there are two electrons in the first shell and seven electrons in the second shell.

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