elements from the same group in the periodic table are chemically reactive in a similar way & elements are all from the first group of the periodic table ->  elements from the first group are chemically reactive in a similar way  elements from the first group are chemically reactive in a similar way & if the elements have similar chemical reactivity , then the elements will react with other elements in a similar way ->  elements from the first group will react with other elements in a similar way  elements from the first group will react with other elements in a similar way & oxygen is a kind of element -> elements from the first group will react with oxygen in a similar way