What you initially see dividing one cell from another are the gridlines. Borders allow you to put more solid boxes or other styles of boxes around the cells. They are known as Borders.
When typing reaches the right border of a cell in a table, wordwrap
row
The rows on the periodic table are called periods
The cell borders are highlighted, or if a range of cells are selected, the active cell will be a different colour than the others, usually being white. The name of the active cell will always appear in the name box.
That's commonly called a border. Borders can be as thin as one pixel, or as thick as you want !
In HTML and CSS, a cell border is the border around a table cell. It's best to style borders of cells in a table using CSS to specify what the border should look like, and how much space should surround the content within the cells. Cramped content and large borders decrease legibility, making the data harder to understand.
I found answer on my own,,,, OPEN table
A cell. In the Periodic Table an element fills that cell.
A cell.
A cell as in B7.
Cell
A cell.
A cell.
cell
A cell.
You can do that with table, Insert - Table. Table can have visible or invisible borders, Design tab (appears when you insert or draw table) Table Styles section - Borders.