Part a add single electrons and/or electron pairs as needed to complete the electron-dot symbol for astatine, at. to return the atom to its original state, use the reset button. click to select an electron-pair or single electron, then click on the element symbol to add electrons. click the reset button to clear all electrons and start over. view available hint(s) aannn

7 valence electrons

Explanation:

Astatine has the atomic number 85. Thus, its electron configuration is:

[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵

As we can see, in the last level (6) it has 2 + 5 = 7 electrons, that is, astatine has 7 electrons in its valence shell. In the Lewis dot structure (attached) we write 3 pairs of electrons and 1 unpaired electron around the symbol of At.

adding or remove a gaseous reactant or product changes the concentrations. if the concentration of reactant or product is increased, the system will shift away from the side in which concentration was increased (i.e. if the concentration of reactants is increased, the system will shift toward the products. if more products are added, the system will shift to form more reactants). conversely, if the concentration of reactant or product is decreased, the system will shift toward the side in which concentration was decreased (i.e. if reactants are removed, the system will shift to form more reactants. if the concentration of products is decreased, the equilibrium will shift toward the products).

explanation: