Write the hyphen notation for the element that contains 15 electrons and 15 neutrons. 1. Copper-60 2. Oxygen-15 3. Phosphorus-30 4. Sulfur-31 5. Silicon-30 6. Zinc-60 7. Phosphorus-31 8. Fluorine-15

Phosphorus-30

Explanation:

In hyphen notation, the mass number is written after the name of the element. An element that has 15 electrons and 15 neutrons would also contain 15 protons. Since the mass number of an element is the sum of the protons and neutrons in an atom of that element, the mass number of this element is 30.

Also, the number of protons (or electrons for a neutral atom) present in an atom of that element is known as the atomic number of that element.

In the periodic table of elements, the element with atomic number 15 is phosphorus. Thus, phosphorus has 15 protons, 15 electrons and 15 neutrons. Its mass number = 30. In hyphen notation, it is written as: Phosphorus-30

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation:

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)