When an electron quickly occupies an strength state increased than its ground state, it is in an excited state. An electron can end up excited if it is given greater energy, such as if it absorbs a photon, or packet of light, or collides with a close by atom or particle.
Thrust acts on the spacecraft and propels in the space.
<h3>How space shuttles move?</h3>
1. The force created by the shuttle's engines in expelling the burning fuel produces an equal thrust in the opposite direction. This thrust acts on the spacecraft and propels in the space.
2. The thermosphere and the stratosphere are our hottest atmosphere layers because these two layers are present near the sun as compared to other layers of atmosphere.
3. When the meteors hit the atmosphere, meteors rub against air particles and create friction which is heating the meteors. The heat vaporizes most meteors, creating what we call shooting stars.
Learn more about atmosphere here: brainly.com/question/24925283
Electrons in an atom can be classified as core electrons and valence electrons. Valence electrons are those electrons which are present in valence shell and participates in bond formation. While, Core electrons are all remaining electrons which are not present in valence shell, hence not take part in bonding.
Atomic number of Selenium (Se) is 34 hence it has 34 electrons with following electronic configuration;
1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁴
From electronic configuration it is found that the valence shell is 4, and the number of electrons present in valence shell are 6. So,
Core Electrons = Total Electrons - Valence Electrons
Core Electrons = 34 - 6
Core Electrons = 28
Result:
There are 28 core electrons in Selenium.