What is first and second element of the periodic table?

2 answers:

7 0

The elements on the periodic table are listed in increasing atomic number.

Hydrogen is the first element, and has an A.N. of 1. Also, its very interesting how it doesn't need 8 valence electrons to be stable.

The second element is Helium, which has an A.N (atomic number) of two.

WINSTONCH [101]3 years ago

6 0

Hydrogen= First element,H

Helium=Second Element,He

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At standard temperature and pressure. 0.500 mole of xenon gas occupies

ANEK [815]

Answer:

0.500 mole of Xe (g) occupies 11.2 L at STP.

General Formulas and Concepts:

Gas Laws

STP (Standard Conditions for Temperature and Pressure) = 22.4 L per mole at 1 atm, 273 K

Stoichiometry

Mole ratio
Dimensional Analysis

Explanation:

Step 1: Define

Identify.

0.500 mole Xe (g)

Step 2: Convert

[DA] Set up: $\displaystyle 0.500 \ \text{mole Xe} \bigg( \frac{22.4 \ \text{L Xe}}{1 \ \text{mole Xe}} \bigg)$
[DA] Evaluate: $\displaystyle 0.500 \ \text{mole Xe} \bigg( \frac{22.4 \ \text{L Xe}}{1 \ \text{mole Xe}} \bigg) = 11.2 \ \text{L Xe}$