A helium atom has a smaller atomic radius than the hydrogen atom. Explain why.
Hydrogen has one proton and one electron, whereas Helium has two (protons and electrons). But they are both in the same period (energy level) so their average distance from the nucleus is the same. As you travel along a period from left to right, the atomic number increases, but the valence electrons remain in the same shell. Therefore due to the increasing nuclear charge (pulling electrons closer to the nucleus) the atomic radius decreases from left to right. Therefore He has a smaller atomic radius than H.
Well, you see, the helium atom is a bit of a diva in the atomic world. It likes to keep things tight and compact. It's like the Marie Kondo of atoms - always searching for that perfect atomic organization. So, naturally, it has a smaller atomic radius than hydrogen, which just wants to spread out and make friends with everyone. It's a classic case of helium showing off its minimalist tendencies while hydrogen is out there trying to socialize with everyone. It's atomic personality, I tell you!
The atomic radius of an atom is determined by the distance between the nucleus and the outermost electron shell. In the case of a helium atom, it has two protons in its nucleus, whereas a hydrogen atom only has one proton. Both atoms have the same number of electrons in their outermost shell, which is one.
The smaller atomic radius of a helium atom compared to a hydrogen atom can be attributed to the effect of nuclear charge. Helium has two protons in its nucleus, creating a stronger positive charge in the nucleus compared to hydrogen's single proton. This stronger positive charge exerts a greater pull on the electrons, resulting in a tighter electron cloud and a smaller atomic radius.
Additionally, because helium has a full electron shell with two electrons, it experiences a greater degree of electron-electron repulsion compared to hydrogen, which only has one electron in its outer shell. This repulsion between electrons in helium also contributes to a smaller atomic radius as the electrons spread out more to minimize repulsion forces.
Therefore, the combination of increased nuclear charge and greater electron-electron repulsion results in a smaller atomic radius for helium compared to hydrogen.
To understand why a helium atom has a smaller atomic radius than a hydrogen atom, we need to discuss the factors that determine atomic radius.
Atomic radius is the distance between the nucleus of an atom and its outermost electron shell. It can vary depending on the number of electrons and the electron configuration.
In the case of a hydrogen atom, it has only one electron that occupies the 1s orbital. The 1s orbital is the closest to the nucleus and represents the first energy level. Since hydrogen has only one electron, it occupies its outermost electron shell, resulting in a larger atomic radius.
On the other hand, helium has two electrons. The first electron also occupies the 1s orbital, and the second electron occupies the same orbital but with opposite spin due to the Pauli Exclusion Principle. This arrangement is called a filled electron shell configuration, which is highly stable. The filled electron shell makes the helium atom more compact, causing the atomic radius to be smaller than that of hydrogen.
In summary, the smaller atomic radius of a helium atom compared to a hydrogen atom is due to the presence of two electrons in helium, resulting in a filled electron shell configuration.