Help with number two ASAP.

Halley's comet will next appear in the night sky in the year 2062.

Explanation:

It orbits the sun every 75-76 years, so this is the time between appearances. Halley's comet was recorded by Edmund Halley in 1682. It was seen again in 1758, 1835, 1910, and 1986.

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3