Explanation:
I think the answer is 2nd
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.
Because in difrent materials atoms are more compact or less compact.if they are less compact then it will be easear for them to move
Answer:
Molecular compounds consist of two or more nonmetals. The nonmetals that make up a molecular compound are held together by covalent/molecular bonds. Covalent bonds is known as the "sharing" of valence electrons between two or more chemical species. Valence electrons are shared so that the atoms of the compound can become stable, much like how ionic bonds transfer valence electrons between atoms to achieve stability.
Answer:
Carbon dioxide and water I believe because it is a combustion reaction