Answer:
The distance from Earth to the sun is called an astronomical unit, or AU, which is used to measure distances throughout the solar system.
Answer:
= 25 g
Explanation:
Using the formula;
A = A₀ (1/2)^(t/h)
where A is the final amount,
A₀ is the initial amount of the substance,
t is the time and
h is the half-life of the substance,
In this case; the half life of U-238 h is equal to 4.47 billion years.
A = A₀ (1/2)^(t/h)
A = 50 (1/2)^(4.5 / 4.47)
= 24.88
<u> = 25 g</u>
Positive charge the proton give to the nucleus center of an atom
Explanation:
12)
a) Sodium + oxygen = ?
When sodium reacts oxygen its forms sodium oxide as a product.
b) magnesium + fluorine = ?
When magnesium reacts with fluorine its forms magnesium fluoride as a product.
13)
a) 
Decomposition of mercury(II) oxide on heating gives out mercury and oxygen gas.
b)
The electrolytic decomposition of water gives out hydrogen gas amd oxygen gas.
Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties. Major periodic trends include: electronegativity, ionization energy, electron affinity, atomic radius, melting point, and metallic character. Periodic trends, arising from the arrangement of the periodic table, provide chemists with an invaluable tool to quickly predict an element's properties. These trends exist because of the similar atomic structure of the elements within their respective group families or periods, and because of the periodic nature of the elements.
