La estructura del hielo, forma un retículo que ocupa más espacio y es menos denso que el agua líquida. Cuando el agua se enfría, se contrae su volumen, como sucede en todos los cuerpos, pero al alcanzar los 4ºC cesa la contracción y su estructura se dilata hasta transformarse en hielo en el punto de congelación. Por eso el hielo es menos denso que el agua y flota sobre ella. Gracias a esta anomalía del agua, los lagos, ríos y mares, comienzan a congelarse desde la superficie hacia abajo, y esta costra de hielo superficial sirve de abrigo a los seres que viven, pues aunque la temperatura ambiental sea extremadamente baja (-50 0 -60º C), el agua de la superficie transformada en hielo mantiene constante su temperatura en 0ºC. Y el agua del fondo queda protegida térmicamente del exterior, y puede alcanzar los 4º o 5ºC, que son suficientes para la supervivencia de ciertas especies. En esta propiedad se basan los esquimales para construir sus casa de hielo (iglúes).
Holding
temperature and pressure constant
<span>the
most important feature in determining the phase of a given organic compound is
pressure. ransfers of organic compounds
between phases are controlled by molecular interactions (intermolecular bonding)
in the two phases between which transfer is occurring. This is governed
by temperature and pressure</span>
Balanced chemical reaction:
2HNO₃<span>(aq) + Sr(OH)</span>₂(aq) → 2H₂O(l) + Sr(NO₃)₂<span>(aq).
Balanced ionic reaction:
2H</span>⁺(aq) + 2NO₃⁻(aq) + Sr²⁺(aq) + 2OH⁻(aq) → 2H₂O(l) + Sr²⁺(aq) + 2NO₃⁻(aq).
Net ionic reaction:
2H⁺(aq) + 2OH⁻(aq) → 2H₂O(l).
(aq) means that substances are dissociated on cations and anions in water.
Atomic mass Cu = 63.546 a.m.u
63.546 g ---------------- 6.02x10²³ atoms
22 g --------------------- ??
22 x (6.02x10²³ ) / 63.546 => 2.08x10²³ atoms
hope this helps!
The electron configuration filling patterns of some elements in group 6b(6) and group 1b(11) reflect the increasing stability of half-filled and completely filled sublevels.
<h2>
What is electronic configuration?</h2>
The distribution of electrons in an element's atomic orbitals is described by the element's electron configuration. Atomic subshells that contain electrons are placed in a series, and the number of electrons that each one of them holds is indicated in superscript for all atomic electron configurations. For instance, sodium's electron configuration is 1s22s22p63s1.
Almost all of the elements write their electronic configurations in the same style. When the energies of two subshells differ, an electron from the lower energy subshell occasionally goes to the higher energy subshell.
This is due to two factors:
Symmetrical distribution: As is well known, stability is a result of symmetry. Because of the symmetrical distribution of electrons, orbitals where the sub-shell is exactly half-full or totally filled are more stable.
Energy exchange: The electrons in degenerate orbitals have a parallel spin and are prone to shifting positions. The energy released during this process is simply referred to as exchange energy. The greatest number of exchanges occurs when the orbitals are half- or fully-filled. Its stability is therefore at its highest.
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