Which property do all elements in a row of the periodic table have in common?

1. number of orbitals
2. number of protons
3. number of neutrons
4. number of valence electrons

2. number of protons

Which property do all elements in a row of the periodic table have in common?

4. number of valence electrons

The property that all elements in a row of the periodic table have in common is the number of valence electrons (option 4).

The property that all elements in a row of the periodic table have in common is the number of valence electrons.

To understand why this is the case, let's break down each option:

1. Number of orbitals: An orbital is a region in an atom where an electron is most likely to be found. The number of orbitals depends on the specific energy level an electron occupies, which varies across rows of the periodic table. Therefore, this option is not correct.

2. Number of protons: The number of protons in the nucleus of an atom determines the element's atomic number and identity. While the number of protons does increase as you move across a row, not all elements in a row have the same number of protons. Therefore, this option is not correct.

3. Number of neutrons: Neutrons are particles found in the nucleus of an atom that have no charge. The number of neutrons can vary within an element, resulting in different isotopes. Since not all elements in a row have the same number of neutrons, this option is not correct either.

4. Number of valence electrons: Valence electrons are the electrons in the outermost shell (energy level) of an atom. These are the electrons involved in chemical bonding and determining an element's chemical properties. In a row of the periodic table, elements have the same number of energy levels (shells), so the number of valence electrons is the same across that row. Therefore, this is the correct option – all elements in a row have the same number of valence electrons.

By understanding the periodic table's organization, specifically the arrangement of elements into rows and columns, we can determine that the number of valence electrons is the property shared among all elements in a row.