Answer:
calcium
Explanation:
if you have a periodic table that would be very helpful to you
Answer:
2. The hydrogen atom has quantized energy levels.
Explanation:
The Bohr model of the atom states that the structure of the atom is quantized, that is, that electrons can only orbit the nucleus in specific orbits with a fixed radius. Therefore, the electron cannot be in energy levels that do not correspond to these quantized levels.
Answer:

Explanation:
Let assume that ball begins its movement at a height of zero. The height can be found by energy approach, to be precise, by Principle of Energy Conservation:


YES I WILL HELP YOU SO MUCH
Answer:
YES
Explanation:
An echo may be defined as a sound which is repeated because of the sound waves that are produced are reflected back after striking a surface. Sound waves can smoothly bounce off the hard objects in the same manner as a rubber ball bounces back the ground.
When a sound wave strikes a hard surface, the sound waves gets reflected back and bounces back to the observer and produces an echo. If the sound waves strikes a soft surface it absorbs the sound.
Although the direction of a sound changes but the echo sounds in the same way as the original sound.