Answer:
About 60.
Explanation:
Mendeleev knew of 63 elements. He wrote their properties on cards and arranged them in order of atomic mass.
That's how he discovered that the properties of elements are periodic functions of their atomic masses.
Answer:
The 3R rule states that Radial cracks form a Right angle on the Reverse side of the force. This rule enables an examiner to determine readily the side on which a window or pane of glass was broken.
I hope it's helpful!
Answer:
A
Explanation:
because B is wrong as it doesn't have the same mass number. C is wrong as it has different number of neutrons. D is wrong as it has more neutrons than protons.
Dipyrithione is a chemical with formula, C₁₀H₈N₂O₂S₂. This means that each molecule of the substance has two (2) atoms of nitrogen. By using the dimensional analysis and Avogadro's number, equal to 6.022 x 10²³, we calculate for the answer as shown below.
n = (8.2 x 10²⁴ atoms N)(1 molecule dipyrithione/ 2 atoms of N)(1 mole dipyrithione/ 6.022 x 10²³ molecules dipyrithione)
Simplifying,
n = 6.8 moles dipyrithione
<em>ANSWER: 6.8 moles</em>
Answer:
Explanation:
Step 1. Identify the Group that contains X
We look at the consecutive ionization energies and hunt for a big jump between them
We see a big jump between n = 2 and n = 3. This indicates that X has two valence electrons.
We can easily remove two electrons, but the third electron requires much more energy. That electron must be in the stable, filled, inner core.
So, X is in Group 2 and P is in Group 15.
Step 2. Identify the Compound
X can lose two valence electrons to reach a stable octet, and P can do the same by gaining three electrons.
We must have 3 X atoms for every 2 P atoms.
The formula of the compound is 
.
