<span>The scientists discovered that when they organized elements in order of increasing atomic mass there is a pattern of repetition of properties (A). The periodic law was developed by Dmitri Mendeleev and Lothar Mayer in 1869. They worked independently of each other and both created a periodic table. They both arranged the items on the table by weight and both suggested that certain properties of the elements recur. The Mendeleev table is the most important table because the values for the atomic mass are the most accurate.</span>
The change in pressure over a given distance is defined as a pressure gradient. The strength of this pressure gradient determines how fast the wind moves from higher pressure toward lower pressure. A stronger pressure gradient will cause stronger winds, as shown in Figure 2. >> Balanced in the vertical by the force of gravity
They are examples of elements.
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Oxygen-16 is the atom in question.
- Atomic number: 8.
- Mass number: 16.
<h3>Explanation</h3>
The superscript of the ion says "2-". That means that the ion here carries a charge of -2.
- The charge is negative, meaning that there are more electrons (which are negative) than protons (which are positive) in that ion.
- The size of the charge is 2. There are two more electrons than protons in that ion.
There are 10 electrons in total in that ion. There are two more electrons than protons. That means that there are 10 - 2 = 8 protons in that ion.
The atomic number of an atom is the same as its number of protons. The atomic number of X is 8.
The atomic number determines the element. Atomic number 8 is oxygen. Thus element X is oxygen.
Mass number is the sum of number of protons and neutrons in an atom. 8 + 8 = 16 for this atom.