To which group in the periodic table does lithium belong? How many valence electrons does it have?
Lithium is an alkali metal (column one) and has one valence electron.
The groups of the periodic table are organized in columns (from top to bottom) and some have specific names, while some are part of a larger grouping. For example, group one is the alkali metals and consists of Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium. All members of this group share common characteristics, an example being how all alkali metals react with water.
In order to find how many valence electrons exist, you will need to understand how electron shells work. I would suggest finding a more in-depth explanation of electron shells to help with any questions you may still have. Basically, the electrons that surround an atom can exist in a few different types of orbitals: s, p d, and f. s orbitals can hold up to two electrons, p orbitals can hold up to six, d orbitals can hold ten, and f orbitals up to 14.
Electrons want to reside in the orbital closest to the atom (and thus at the lowest energy state). Here is the order of orbitals in terms of energy states: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p and so on.
Lithium is the third element, meaning it has three protons and with a neutral charge must have 3 electrons. So now we fill the orbitals from lowest energy to highest with our three electrons. the 1s orbital can hold two of the three electrons, so that now becomes a filled electron orbital and does not count towards valence electrons. The next lowest energy orbital is 2s, and we have one electron left. The 2s orbital now has one electron, which is lithium's only valence electron.
Note: I am new to this website and am just a high school chemistry student, so please don't take my explanation as the only correct one. If you're still confused on this topic, Sal Khan from khan academy has an excellent video on the topic as well. Here's the link: https://www.khanacademy.org/science/biology/chemistry--of-life/electron-shells-and-orbitals/v/orbitals. Let me know if I helped!