how can you tell how many valence electrons family 3 (transition metals) have?

im confused about this.

I am unsure how you are using family. Do you mean period 3 (period 3 elements are Na, Mg, Al, Si, P, S, Cl, and Ar. Group 3 (or Group III)(or group 13)consists of B, Al, Ga, In, and Tl.

In the first case, the number of valence electrons consists of the outside electrons and in this case that is the group number; i.e., Na has 1 for it is in group IA, Mg has 2 for it is in group IIA, Al has 3 for it is in group IIIA, etc. If the latter case B, Al, Ga, In and Tl have 3 electrons in their outer shell(s) and they have a valence of 3. (Thalium also exhibits a +1 valence in some of its compounds). If you mean transition metals, they are neither period 3 nor group 3. The first transition series (the 3d series) is in period 4. This scenario can be confusing for the number of valence electrons for they vary. One way to make an educated guess is to look at the electron configuration. They are as follows:
Scandium is [Ar] 3d1 4s2
Titanium is [Ar] 3d2 4s2
Vanadium is [Ar] 3d3 4s2
Chromium is [Ar] 3d5 4s1
etc.
You could make a case for Sc as +3 and it is. The last three electrons are the outside ones.
You could make a case for Ti being +2 or +4. Actually it has common valences of +3 and 4. For V, one could make the case for +2 and +5 whereas it is commonly 2,3,4, and 5. So the number of so-called valence electrons depends upon what anion it is combining with and how many of those d electrons are drawn away. Educated guesses help a little; memorizing does the rest. Experience doesn't hurt anything.

To determine the number of valence electrons for transition metals in family 3, you need to consider their electron configuration.

Transition metals have a unique electron configuration due to the filling of their d orbitals. In the case of family 3, it includes elements such as titanium (Ti), vanadium (V), chromium (Cr), and so on. Since these elements are in the transition metal region of the periodic table, their electron configurations may deviate from the simple valence electron count.

Here's a general method to determine the number of valence electrons for transition metals:

1. Locate the element in the periodic table. For example, titanium (Ti) is in the 3rd period and is in group 4.

2. Determine the electron configuration. For transition metals, the electrons first fill the inner d orbitals before the outer s and p orbitals.

3. Calculate the total number of electrons in the outermost energy level (principle quantum number "n"). In the case of transition metals, it is the highest energy level (n value) that contains electrons. For example, titanium has the electron configuration [Ar] 3d² 4s². Here, the outermost energy level is 4, so we count the electrons in the 4s and 3d orbitals.

4. Subtract the number of electrons in the d orbitals from the total number of electrons in the outermost energy level. Valence electrons mainly participate in chemical bonding and reactions.

For example, in the case of titanium (Ti), there are 2 electrons in the 4s orbital and 2 electrons in the 3d orbital. Subtracting the 2 electrons in the 3d orbital from the total of 4 electrons in the 4s and 3d orbitals gives us 2 valence electrons for titanium.

It's important to remember that the number of valence electrons for transition metals can vary since they have multiple oxidation states and can lose or gain different numbers of electrons. Nevertheless, following these steps will help you determine the valence electrons based on their electron configuration.