Which element has 8 valance electrons and 4 energy levels

True or false when elements combine to form a mixture, the resulting chemical properties may be very different from those of the elements that make it.

Aheat engine that operates on a carnot cycle has an efficiency of 0.420 when its low-temperature reservoir is at 10 ∘c.part aby how many degrees celsius must you increase the temperature of the high-temperature reservoir to increase the efficiency to 0.600 if you continue to use the same low-temperature reservoir?

The ima of the following pulley system is