Table of Contents
How our scientist came up with an idea that what Dmitri Mendeleev created as his periodic table is missing some elements?
Mendeleev went even further. He corrected the known atomic masses of some elements and he used the patterns in his table to predict the properties of the elements he thought must exist but had yet to be discovered. He left blank spaces in his chart as placeholders to represent those unknown elements.
How old is our universe?
about 13.8 billion years old
Scientists’ best estimate is that the universe is about 13.8 billion years old.
How do we know what elements are in the universe?
Each element absorbs light at specific wavelengths unique to that atom. When astronomers look at an object’s spectrum, they can determine its composition based on these wavelengths. The most common method astronomers use to determine the composition of stars, planets, and other objects is spectroscopy.
What did Dmitri Mendeleev discover?
Petersburg, Russia), Russian chemist who developed the periodic classification of the elements. Mendeleev found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements.
How did hydrogen form in the universe?
Hydrogen didn’t appear until the universe had spread out — and subsequently cooled — enough for the first protons and neutrons, and later simple atoms, to form. Within about 3 minutes after the Big Bang, conditions cooled enough for these protons and neutrons to form hydrogen nuclei.
How do scientists know how old the universe is?
Astronomers estimate the age of the universe in two ways: 1) by looking for the oldest stars; and 2) by measuring the rate of expansion of the universe and extrapolating back to the Big Bang; just as crime detectives can trace the origin of a bullet from the holes in a wall.
How do they know how old Earth is?
4.543 billion years
Earth/Age
By dating the rocks in Earth’s ever-changing crust, as well as the rocks in Earth’s neighbors, such as the moon and visiting meteorites, scientists have calculated that Earth is 4.54 billion years old, with an error range of 50 million years.